The document discusses code for serial port (com) device drivers in FreeBSD. It shows code from the comstart() function, which is called by the tty layer when there is outgoing data to transmit. Comstart() grabs the data from the tty queue and sets up the com_softc structure to start transmission. It then calls the chip-specific transmit function. The com_softc structure contains a pointer to the associated tty structure.

1. start_printf: dev/ic/com.c
comstart()
start_printf: dev/ic/com.c
comstart()
start_printf: dev/ic/com.c
comstart()
start_printf: dev/ic/com.c
comstart()
start_printf: dev/ic/com.c
comstart()
Kiwamu OkabeKiwamu OkabeKiwamu OkabeKiwamu OkabeKiwamu Okabe

2. Where comstart called?Where comstart called?Where comstart called?Where comstart called?Where comstart called?
Who kick "tp->t_oproc"?Who kick "tp->t_oproc"?Who kick "tp->t_oproc"?Who kick "tp->t_oproc"?Who kick "tp->t_oproc"?
// File: sys/dev/ic/com.c
void
com_attach_subr(struct com_softc *sc)
{
// -- snip --
fifodone:
tp = tty_alloc();
tp->t_oproc = comstart;
// File: sys/dev/ic/com.c
void
com_attach_subr(struct com_softc *sc)
{
// -- snip --
fifodone:
tp = tty_alloc();
tp->t_oproc = comstart;
// File: sys/dev/ic/com.c
void
com_attach_subr(struct com_softc *sc)
{
// -- snip --
fifodone:
tp = tty_alloc();
tp->t_oproc = comstart;
// File: sys/dev/ic/com.c
void
com_attach_subr(struct com_softc *sc)
{
// -- snip --
fifodone:
tp = tty_alloc();
tp->t_oproc = comstart;
// File: sys/dev/ic/com.c
void
com_attach_subr(struct com_softc *sc)
{
// -- snip --
fifodone:
tp = tty_alloc();
tp->t_oproc = comstart;

3. com0 attached at isa0com0 attached at isa0com0 attached at isa0com0 attached at isa0com0 attached at isa0
$ grep 3f8 sys/arch/i386/conf/GENERIC | grep com0
com0 at isa? port 0x3f8 irq 4 # Standard PC serial ports
$ grep -B 1 dev/isa/com_isa.c sys/dev/isa/files.isa
attach com at isa with com_isa
file dev/isa/com_isa.c com_isa
$ grep 3f8 sys/arch/i386/conf/GENERIC | grep com0
com0 at isa? port 0x3f8 irq 4 # Standard PC serial ports
$ grep -B 1 dev/isa/com_isa.c sys/dev/isa/files.isa
attach com at isa with com_isa
file dev/isa/com_isa.c com_isa
$ grep 3f8 sys/arch/i386/conf/GENERIC | grep com0
com0 at isa? port 0x3f8 irq 4 # Standard PC serial ports
$ grep -B 1 dev/isa/com_isa.c sys/dev/isa/files.isa
attach com at isa with com_isa
file dev/isa/com_isa.c com_isa
$ grep 3f8 sys/arch/i386/conf/GENERIC | grep com0
com0 at isa? port 0x3f8 irq 4 # Standard PC serial ports
$ grep -B 1 dev/isa/com_isa.c sys/dev/isa/files.isa
attach com at isa with com_isa
file dev/isa/com_isa.c com_isa
$ grep 3f8 sys/arch/i386/conf/GENERIC | grep com0
com0 at isa? port 0x3f8 irq 4 # Standard PC serial ports
$ grep -B 1 dev/isa/com_isa.c sys/dev/isa/files.isa
attach com at isa with com_isa
file dev/isa/com_isa.c com_isa
// File: sys/dev/isa/com_isa.c
void
com_isa_attach(device_t parent, device_t self, void *aux)
{
// -- snip --
com_attach_subr(sc);
// File: sys/dev/isa/com_isa.c
void
com_isa_attach(device_t parent, device_t self, void *aux)
{
// -- snip --
com_attach_subr(sc);
// File: sys/dev/isa/com_isa.c
void
com_isa_attach(device_t parent, device_t self, void *aux)
{
// -- snip --
com_attach_subr(sc);
// File: sys/dev/isa/com_isa.c
void
com_isa_attach(device_t parent, device_t self, void *aux)
{
// -- snip --
com_attach_subr(sc);
// File: sys/dev/isa/com_isa.c
void
com_isa_attach(device_t parent, device_t self, void *aux)
{
// -- snip --
com_attach_subr(sc);

4. com softc has struct tty membercom softc has struct tty membercom softc has struct tty membercom softc has struct tty membercom softc has struct tty member
// File: sys/dev/ic/com.c
void
com_attach_subr(struct com_softc *sc)
{
// -- snip --
tp = tty_alloc();
tp->t_oproc = comstart;
tp->t_param = comparam;
tp->t_hwiflow = comhwiflow;
sc->sc_tty = tp;
// -- snip --
tty_attach(tp);
// File: sys/dev/ic/com.c
void
com_attach_subr(struct com_softc *sc)
{
// -- snip --
tp = tty_alloc();
tp->t_oproc = comstart;
tp->t_param = comparam;
tp->t_hwiflow = comhwiflow;
sc->sc_tty = tp;
// -- snip --
tty_attach(tp);
// File: sys/dev/ic/com.c
void
com_attach_subr(struct com_softc *sc)
{
// -- snip --
tp = tty_alloc();
tp->t_oproc = comstart;
tp->t_param = comparam;
tp->t_hwiflow = comhwiflow;
sc->sc_tty = tp;
// -- snip --
tty_attach(tp);
// File: sys/dev/ic/com.c
void
com_attach_subr(struct com_softc *sc)
{
// -- snip --
tp = tty_alloc();
tp->t_oproc = comstart;
tp->t_param = comparam;
tp->t_hwiflow = comhwiflow;
sc->sc_tty = tp;
// -- snip --
tty_attach(tp);
// File: sys/dev/ic/com.c
void
com_attach_subr(struct com_softc *sc)
{
// -- snip --
tp = tty_alloc();
tp->t_oproc = comstart;
tp->t_param = comparam;
tp->t_hwiflow = comhwiflow;
sc->sc_tty = tp;
// -- snip --
tty_attach(tp);
// File: sys/dev/ic/comvar.h
struct com_softc {
device_t sc_dev;
void *sc_si;
struct tty *sc_tty;
// File: sys/dev/ic/comvar.h
struct com_softc {
device_t sc_dev;
void *sc_si;
struct tty *sc_tty;
// File: sys/dev/ic/comvar.h
struct com_softc {
device_t sc_dev;
void *sc_si;
struct tty *sc_tty;
// File: sys/dev/ic/comvar.h
struct com_softc {
device_t sc_dev;
void *sc_si;
struct tty *sc_tty;
// File: sys/dev/ic/comvar.h
struct com_softc {
device_t sc_dev;
void *sc_si;
struct tty *sc_tty;

5. Maybe call tree is...Maybe call tree is...Maybe call tree is...Maybe call tree is...Maybe call tree is...
cdev_write
=> comwrite
=> ttwrite
=> ttstart
=> comstart
cdev_write
=> comwrite
=> ttwrite
=> ttstart
=> comstart
cdev_write
=> comwrite
=> ttwrite
=> ttstart
=> comstart
cdev_write
=> comwrite
=> ttwrite
=> ttstart
=> comstart
cdev_write
=> comwrite
=> ttwrite
=> ttstart
=> comstart

6. comwrite()comwrite()comwrite()comwrite()comwrite()
#define COM_ISALIVE(sc) ((sc)->enabled != 0 &&
device_is_active((sc)->sc_dev))
int
comwrite(dev_t dev, struct uio *uio, int flag)
{
struct com_softc *sc =
device_lookup_private(&com_cd, COMUNIT(dev));
struct tty *tp = sc->sc_tty;
if (COM_ISALIVE(sc) == 0)
return (EIO);
return ((*tp->t_linesw->l_write)(tp, uio, flag));
}
#define COM_ISALIVE(sc) ((sc)->enabled != 0 &&
device_is_active((sc)->sc_dev))
int
comwrite(dev_t dev, struct uio *uio, int flag)
{
struct com_softc *sc =
device_lookup_private(&com_cd, COMUNIT(dev));
struct tty *tp = sc->sc_tty;
if (COM_ISALIVE(sc) == 0)
return (EIO);
return ((*tp->t_linesw->l_write)(tp, uio, flag));
}
#define COM_ISALIVE(sc) ((sc)->enabled != 0 &&
device_is_active((sc)->sc_dev))
int
comwrite(dev_t dev, struct uio *uio, int flag)
{
struct com_softc *sc =
device_lookup_private(&com_cd, COMUNIT(dev));
struct tty *tp = sc->sc_tty;
if (COM_ISALIVE(sc) == 0)
return (EIO);
return ((*tp->t_linesw->l_write)(tp, uio, flag));
}
#define COM_ISALIVE(sc) ((sc)->enabled != 0 &&
device_is_active((sc)->sc_dev))
int
comwrite(dev_t dev, struct uio *uio, int flag)
{
struct com_softc *sc =
device_lookup_private(&com_cd, COMUNIT(dev));
struct tty *tp = sc->sc_tty;
if (COM_ISALIVE(sc) == 0)
return (EIO);
return ((*tp->t_linesw->l_write)(tp, uio, flag));
}
#define COM_ISALIVE(sc) ((sc)->enabled != 0 &&
device_is_active((sc)->sc_dev))
int
comwrite(dev_t dev, struct uio *uio, int flag)
{
struct com_softc *sc =
device_lookup_private(&com_cd, COMUNIT(dev));
struct tty *tp = sc->sc_tty;
if (COM_ISALIVE(sc) == 0)
return (EIO);
return ((*tp->t_linesw->l_write)(tp, uio, flag));
}

7. comstart() #1comstart() #1comstart() #1comstart() #1comstart() #1
void
comstart(struct tty *tp)
{
struct com_softc *sc =
device_lookup_private(&com_cd, COMUNIT(tp->t_dev));
struct com_regs *regsp = &sc->sc_regs;
int s;
if (COM_ISALIVE(sc) == 0)
return;
s = spltty();
if (ISSET(tp->t_state, TS_BUSY | TS_TIMEOUT | TS_TTSTOP))
goto out;
if (sc->sc_tx_stopped)
goto out;
if (!ttypull(tp))
goto out;
void
comstart(struct tty *tp)
{
struct com_softc *sc =
device_lookup_private(&com_cd, COMUNIT(tp->t_dev));
struct com_regs *regsp = &sc->sc_regs;
int s;
if (COM_ISALIVE(sc) == 0)
return;
s = spltty();
if (ISSET(tp->t_state, TS_BUSY | TS_TIMEOUT | TS_TTSTOP))
goto out;
if (sc->sc_tx_stopped)
goto out;
if (!ttypull(tp))
goto out;
void
comstart(struct tty *tp)
{
struct com_softc *sc =
device_lookup_private(&com_cd, COMUNIT(tp->t_dev));
struct com_regs *regsp = &sc->sc_regs;
int s;
if (COM_ISALIVE(sc) == 0)
return;
s = spltty();
if (ISSET(tp->t_state, TS_BUSY | TS_TIMEOUT | TS_TTSTOP))
goto out;
if (sc->sc_tx_stopped)
goto out;
if (!ttypull(tp))
goto out;
void
comstart(struct tty *tp)
{
struct com_softc *sc =
device_lookup_private(&com_cd, COMUNIT(tp->t_dev));
struct com_regs *regsp = &sc->sc_regs;
int s;
if (COM_ISALIVE(sc) == 0)
return;
s = spltty();
if (ISSET(tp->t_state, TS_BUSY | TS_TIMEOUT | TS_TTSTOP))
goto out;
if (sc->sc_tx_stopped)
goto out;
if (!ttypull(tp))
goto out;
void
comstart(struct tty *tp)
{
struct com_softc *sc =
device_lookup_private(&com_cd, COMUNIT(tp->t_dev));
struct com_regs *regsp = &sc->sc_regs;
int s;
if (COM_ISALIVE(sc) == 0)
return;
s = spltty();
if (ISSET(tp->t_state, TS_BUSY | TS_TIMEOUT | TS_TTSTOP))
goto out;
if (sc->sc_tx_stopped)
goto out;
if (!ttypull(tp))
goto out;

8. ttypull()ttypull()ttypull()ttypull()ttypull()
/*
* Try to pull more output from the producer. Return non-zero if
* there is output ready to be sent.
*/
bool
ttypull(struct tty *tp)
{
/* XXXSMP not yet KASSERT(mutex_owned(&tty_lock)); */
if (tp->t_outq.c_cc <= tp->t_lowat) {
cv_broadcast(&tp->t_outcv);
selnotify(&tp->t_wsel, 0, NOTE_SUBMIT);
}
return tp->t_outq.c_cc != 0;
}
/*
* Try to pull more output from the producer. Return non-zero if
* there is output ready to be sent.
*/
bool
ttypull(struct tty *tp)
{
/* XXXSMP not yet KASSERT(mutex_owned(&tty_lock)); */
if (tp->t_outq.c_cc <= tp->t_lowat) {
cv_broadcast(&tp->t_outcv);
selnotify(&tp->t_wsel, 0, NOTE_SUBMIT);
}
return tp->t_outq.c_cc != 0;
}
/*
* Try to pull more output from the producer. Return non-zero if
* there is output ready to be sent.
*/
bool
ttypull(struct tty *tp)
{
/* XXXSMP not yet KASSERT(mutex_owned(&tty_lock)); */
if (tp->t_outq.c_cc <= tp->t_lowat) {
cv_broadcast(&tp->t_outcv);
selnotify(&tp->t_wsel, 0, NOTE_SUBMIT);
}
return tp->t_outq.c_cc != 0;
}
/*
* Try to pull more output from the producer. Return non-zero if
* there is output ready to be sent.
*/
bool
ttypull(struct tty *tp)
{
/* XXXSMP not yet KASSERT(mutex_owned(&tty_lock)); */
if (tp->t_outq.c_cc <= tp->t_lowat) {
cv_broadcast(&tp->t_outcv);
selnotify(&tp->t_wsel, 0, NOTE_SUBMIT);
}
return tp->t_outq.c_cc != 0;
}
/*
* Try to pull more output from the producer. Return non-zero if
* there is output ready to be sent.
*/
bool
ttypull(struct tty *tp)
{
/* XXXSMP not yet KASSERT(mutex_owned(&tty_lock)); */
if (tp->t_outq.c_cc <= tp->t_lowat) {
cv_broadcast(&tp->t_outcv);
selnotify(&tp->t_wsel, 0, NOTE_SUBMIT);
}
return tp->t_outq.c_cc != 0;
}

9. comstart() #2comstart() #2comstart() #2comstart() #2comstart() #2
/* Grab the first contiguous region of buffer space. */
{
u_char *tba;
int tbc;
tba = tp->t_outq.c_cf;
tbc = ndqb(&tp->t_outq, 0);
mutex_spin_enter(&sc->sc_lock);
sc->sc_tba = tba;
sc->sc_tbc = tbc;
}
SET(tp->t_state, TS_BUSY);
sc->sc_tx_busy = 1;
/* Grab the first contiguous region of buffer space. */
{
u_char *tba;
int tbc;
tba = tp->t_outq.c_cf;
tbc = ndqb(&tp->t_outq, 0);
mutex_spin_enter(&sc->sc_lock);
sc->sc_tba = tba;
sc->sc_tbc = tbc;
}
SET(tp->t_state, TS_BUSY);
sc->sc_tx_busy = 1;
/* Grab the first contiguous region of buffer space. */
{
u_char *tba;
int tbc;
tba = tp->t_outq.c_cf;
tbc = ndqb(&tp->t_outq, 0);
mutex_spin_enter(&sc->sc_lock);
sc->sc_tba = tba;
sc->sc_tbc = tbc;
}
SET(tp->t_state, TS_BUSY);
sc->sc_tx_busy = 1;
/* Grab the first contiguous region of buffer space. */
{
u_char *tba;
int tbc;
tba = tp->t_outq.c_cf;
tbc = ndqb(&tp->t_outq, 0);
mutex_spin_enter(&sc->sc_lock);
sc->sc_tba = tba;
sc->sc_tbc = tbc;
}
SET(tp->t_state, TS_BUSY);
sc->sc_tx_busy = 1;
/* Grab the first contiguous region of buffer space. */
{
u_char *tba;
int tbc;
tba = tp->t_outq.c_cf;
tbc = ndqb(&tp->t_outq, 0);
mutex_spin_enter(&sc->sc_lock);
sc->sc_tba = tba;
sc->sc_tbc = tbc;
}
SET(tp->t_state, TS_BUSY);
sc->sc_tx_busy = 1;

10. ndqb()ndqb()ndqb()ndqb()ndqb()
/*
* Return count of contiguous characters in clist.
* Stop counting if flag&character is non-null.
*/
int
ndqb(struct clist *clp, int flag)
{
int count = 0;
int i;
int cc;
int s;
s = spltty();
if ((cc = clp->c_cc) == 0)
goto out;
// --snip--
out:
splx(s);
return count;
}
/*
* Return count of contiguous characters in clist.
* Stop counting if flag&character is non-null.
*/
int
ndqb(struct clist *clp, int flag)
{
int count = 0;
int i;
int cc;
int s;
s = spltty();
if ((cc = clp->c_cc) == 0)
goto out;
// --snip--
out:
splx(s);
return count;
}
/*
* Return count of contiguous characters in clist.
* Stop counting if flag&character is non-null.
*/
int
ndqb(struct clist *clp, int flag)
{
int count = 0;
int i;
int cc;
int s;
s = spltty();
if ((cc = clp->c_cc) == 0)
goto out;
// --snip--
out:
splx(s);
return count;
}
/*
* Return count of contiguous characters in clist.
* Stop counting if flag&character is non-null.
*/
int
ndqb(struct clist *clp, int flag)
{
int count = 0;
int i;
int cc;
int s;
s = spltty();
if ((cc = clp->c_cc) == 0)
goto out;
// --snip--
out:
splx(s);
return count;
}
/*
* Return count of contiguous characters in clist.
* Stop counting if flag&character is non-null.
*/
int
ndqb(struct clist *clp, int flag)
{
int count = 0;
int i;
int cc;
int s;
s = spltty();
if ((cc = clp->c_cc) == 0)
goto out;
// --snip--
out:
splx(s);
return count;
}

11. struct cliststruct cliststruct cliststruct cliststruct clist
/*
* Clists are actually ring buffers. The c_cc, c_cf, c_cl fields
have
* exactly the same behaviour as in true clists.
* if c_cq is NULL, the ring buffer has no TTY_QUOTE functionality
* (but, saves memory and CPU time)
*
* *DON'T* play with c_cs, c_ce, c_cq, or c_cl outside
tty_subr.c!!!
*/
struct clist {
u_char *c_cf; /* points to first character */
u_char *c_cl; /* points to next open character */
u_char *c_cs; /* start of ring buffer */
u_char *c_ce; /* c_ce + c_len */
u_char *c_cq; /* N bits/bytes long, see tty_subr.c */
int c_cc; /* count of characters in queue */
int c_cn; /* total ring buffer length */
};
/*
* Clists are actually ring buffers. The c_cc, c_cf, c_cl fields
have
* exactly the same behaviour as in true clists.
* if c_cq is NULL, the ring buffer has no TTY_QUOTE functionality
* (but, saves memory and CPU time)
*
* *DON'T* play with c_cs, c_ce, c_cq, or c_cl outside
tty_subr.c!!!
*/
struct clist {
u_char *c_cf; /* points to first character */
u_char *c_cl; /* points to next open character */
u_char *c_cs; /* start of ring buffer */
u_char *c_ce; /* c_ce + c_len */
u_char *c_cq; /* N bits/bytes long, see tty_subr.c */
int c_cc; /* count of characters in queue */
int c_cn; /* total ring buffer length */
};
/*
* Clists are actually ring buffers. The c_cc, c_cf, c_cl fields
have
* exactly the same behaviour as in true clists.
* if c_cq is NULL, the ring buffer has no TTY_QUOTE functionality
* (but, saves memory and CPU time)
*
* *DON'T* play with c_cs, c_ce, c_cq, or c_cl outside
tty_subr.c!!!
*/
struct clist {
u_char *c_cf; /* points to first character */
u_char *c_cl; /* points to next open character */
u_char *c_cs; /* start of ring buffer */
u_char *c_ce; /* c_ce + c_len */
u_char *c_cq; /* N bits/bytes long, see tty_subr.c */
int c_cc; /* count of characters in queue */
int c_cn; /* total ring buffer length */
};
/*
* Clists are actually ring buffers. The c_cc, c_cf, c_cl fields
have
* exactly the same behaviour as in true clists.
* if c_cq is NULL, the ring buffer has no TTY_QUOTE functionality
* (but, saves memory and CPU time)
*
* *DON'T* play with c_cs, c_ce, c_cq, or c_cl outside
tty_subr.c!!!
*/
struct clist {
u_char *c_cf; /* points to first character */
u_char *c_cl; /* points to next open character */
u_char *c_cs; /* start of ring buffer */
u_char *c_ce; /* c_ce + c_len */
u_char *c_cq; /* N bits/bytes long, see tty_subr.c */
int c_cc; /* count of characters in queue */
int c_cn; /* total ring buffer length */
};
/*
* Clists are actually ring buffers. The c_cc, c_cf, c_cl fields
have
* exactly the same behaviour as in true clists.
* if c_cq is NULL, the ring buffer has no TTY_QUOTE functionality
* (but, saves memory and CPU time)
*
* *DON'T* play with c_cs, c_ce, c_cq, or c_cl outside
tty_subr.c!!!
*/
struct clist {
u_char *c_cf; /* points to first character */
u_char *c_cl; /* points to next open character */
u_char *c_cs; /* start of ring buffer */
u_char *c_ce; /* c_ce + c_len */
u_char *c_cq; /* N bits/bytes long, see tty_subr.c */
int c_cc; /* count of characters in queue */
int c_cn; /* total ring buffer length */
};

12. struct clist (figure)struct clist (figure)struct clist (figure)struct clist (figure)struct clist (figure)

13. comstart() #3comstart() #3comstart() #3comstart() #3comstart() #3
/* Enable transmit completion interrupts if necessary. */
if (!ISSET(sc->sc_ier, IER_ETXRDY)) {
SET(sc->sc_ier, IER_ETXRDY);
CSR_WRITE_1(regsp, COM_REG_IER, sc->sc_ier);
}
/* Output the first chunk of the contiguous buffer. */
if (!ISSET(sc->sc_hwflags, COM_HW_NO_TXPRELOAD)) {
u_int n;
n = sc->sc_tbc;
if (n > sc->sc_fifolen)
n = sc->sc_fifolen;
CSR_WRITE_MULTI(regsp,COM_REG_TXDATA,sc->sc_tba,n);
sc->sc_tbc -= n;
sc->sc_tba += n;
}
mutex_spin_exit(&sc->sc_lock);
out:
splx(s);
return;
}
/* Enable transmit completion interrupts if necessary. */
if (!ISSET(sc->sc_ier, IER_ETXRDY)) {
SET(sc->sc_ier, IER_ETXRDY);
CSR_WRITE_1(regsp, COM_REG_IER, sc->sc_ier);
}
/* Output the first chunk of the contiguous buffer. */
if (!ISSET(sc->sc_hwflags, COM_HW_NO_TXPRELOAD)) {
u_int n;
n = sc->sc_tbc;
if (n > sc->sc_fifolen)
n = sc->sc_fifolen;
CSR_WRITE_MULTI(regsp,COM_REG_TXDATA,sc->sc_tba,n);
sc->sc_tbc -= n;
sc->sc_tba += n;
}
mutex_spin_exit(&sc->sc_lock);
out:
splx(s);
return;
}
/* Enable transmit completion interrupts if necessary. */
if (!ISSET(sc->sc_ier, IER_ETXRDY)) {
SET(sc->sc_ier, IER_ETXRDY);
CSR_WRITE_1(regsp, COM_REG_IER, sc->sc_ier);
}
/* Output the first chunk of the contiguous buffer. */
if (!ISSET(sc->sc_hwflags, COM_HW_NO_TXPRELOAD)) {
u_int n;
n = sc->sc_tbc;
if (n > sc->sc_fifolen)
n = sc->sc_fifolen;
CSR_WRITE_MULTI(regsp,COM_REG_TXDATA,sc->sc_tba,n);
sc->sc_tbc -= n;
sc->sc_tba += n;
}
mutex_spin_exit(&sc->sc_lock);
out:
splx(s);
return;
}
/* Enable transmit completion interrupts if necessary. */
if (!ISSET(sc->sc_ier, IER_ETXRDY)) {
SET(sc->sc_ier, IER_ETXRDY);
CSR_WRITE_1(regsp, COM_REG_IER, sc->sc_ier);
}
/* Output the first chunk of the contiguous buffer. */
if (!ISSET(sc->sc_hwflags, COM_HW_NO_TXPRELOAD)) {
u_int n;
n = sc->sc_tbc;
if (n > sc->sc_fifolen)
n = sc->sc_fifolen;
CSR_WRITE_MULTI(regsp,COM_REG_TXDATA,sc->sc_tba,n);
sc->sc_tbc -= n;
sc->sc_tba += n;
}
mutex_spin_exit(&sc->sc_lock);
out:
splx(s);
return;
}
/* Enable transmit completion interrupts if necessary. */
if (!ISSET(sc->sc_ier, IER_ETXRDY)) {
SET(sc->sc_ier, IER_ETXRDY);
CSR_WRITE_1(regsp, COM_REG_IER, sc->sc_ier);
}
/* Output the first chunk of the contiguous buffer. */
if (!ISSET(sc->sc_hwflags, COM_HW_NO_TXPRELOAD)) {
u_int n;
n = sc->sc_tbc;
if (n > sc->sc_fifolen)
n = sc->sc_fifolen;
CSR_WRITE_MULTI(regsp,COM_REG_TXDATA,sc->sc_tba,n);
sc->sc_tbc -= n;
sc->sc_tba += n;
}
mutex_spin_exit(&sc->sc_lock);
out:
splx(s);
return;
}

14. clist to serial port (figure)clist to serial port (figure)clist to serial port (figure)clist to serial port (figure)clist to serial port (figure)

15. CSR_WRITE_*()CSR_WRITE_*()CSR_WRITE_*()CSR_WRITE_*()CSR_WRITE_*()
// arch/i386/compile/GENERIC/opt_com.h:
// /* option `COM_REGMAP' not defined */
#define CSR_WRITE_1(r, o, v)
bus_space_write_1((r)->cr_iot, (r)->cr_ioh, o, v)
#define CSR_WRITE_MULTI(r, o, p, n)
bus_space_write_multi_1((r)->cr_iot, (r)->cr_ioh, o, p, n)
#define COM_REG_IER com_ier
#define COM_REG_TXDATA com_data
// arch/i386/compile/GENERIC/opt_com.h:
// /* option `COM_REGMAP' not defined */
#define CSR_WRITE_1(r, o, v)
bus_space_write_1((r)->cr_iot, (r)->cr_ioh, o, v)
#define CSR_WRITE_MULTI(r, o, p, n)
bus_space_write_multi_1((r)->cr_iot, (r)->cr_ioh, o, p, n)
#define COM_REG_IER com_ier
#define COM_REG_TXDATA com_data
// arch/i386/compile/GENERIC/opt_com.h:
// /* option `COM_REGMAP' not defined */
#define CSR_WRITE_1(r, o, v)
bus_space_write_1((r)->cr_iot, (r)->cr_ioh, o, v)
#define CSR_WRITE_MULTI(r, o, p, n)
bus_space_write_multi_1((r)->cr_iot, (r)->cr_ioh, o, p, n)
#define COM_REG_IER com_ier
#define COM_REG_TXDATA com_data
// arch/i386/compile/GENERIC/opt_com.h:
// /* option `COM_REGMAP' not defined */
#define CSR_WRITE_1(r, o, v)
bus_space_write_1((r)->cr_iot, (r)->cr_ioh, o, v)
#define CSR_WRITE_MULTI(r, o, p, n)
bus_space_write_multi_1((r)->cr_iot, (r)->cr_ioh, o, p, n)
#define COM_REG_IER com_ier
#define COM_REG_TXDATA com_data
// arch/i386/compile/GENERIC/opt_com.h:
// /* option `COM_REGMAP' not defined */
#define CSR_WRITE_1(r, o, v)
bus_space_write_1((r)->cr_iot, (r)->cr_ioh, o, v)
#define CSR_WRITE_MULTI(r, o, p, n)
bus_space_write_multi_1((r)->cr_iot, (r)->cr_ioh, o, p, n)
#define COM_REG_IER com_ier
#define COM_REG_TXDATA com_data
// com.c
// = include => dev/ic/comreg.h
// = include => dev/ic/ns16550reg.h
#define com_data 0 /* data register (R/W) */
#define com_ier 1 /* interrupt enable (W) */
// com.c
// = include => dev/ic/comreg.h
// = include => dev/ic/ns16550reg.h
#define com_data 0 /* data register (R/W) */
#define com_ier 1 /* interrupt enable (W) */
// com.c
// = include => dev/ic/comreg.h
// = include => dev/ic/ns16550reg.h
#define com_data 0 /* data register (R/W) */
#define com_ier 1 /* interrupt enable (W) */
// com.c
// = include => dev/ic/comreg.h
// = include => dev/ic/ns16550reg.h
#define com_data 0 /* data register (R/W) */
#define com_ier 1 /* interrupt enable (W) */
// com.c
// = include => dev/ic/comreg.h
// = include => dev/ic/ns16550reg.h
#define com_data 0 /* data register (R/W) */
#define com_ier 1 /* interrupt enable (W) */
The com_data address should be 0x3f8.The com_data address should be 0x3f8.The com_data address should be 0x3f8.The com_data address should be 0x3f8.The com_data address should be 0x3f8.

16. bus_space_map()bus_space_map()bus_space_map()bus_space_map()bus_space_map()
int comcnattach(bus_space_tag_t iot, bus_addr_t iobase, int rate,
int frequency, int type, tcflag_t cflag)
{
// --snip--
regs.cr_iot = iot;
regs.cr_iobase = iobase;
regs.cr_nports = COM_NPORTS;
return comcnattach1(&regs, rate, frequency, type, cflag);
// --snip--
int comcnattach1(struct com_regs *regsp, int rate, int frequency,
int type, tcflag_t cflag)
{
// --snip--
comcons_info.regs = *regsp;
res = cominit(&comcons_info.regs, rate, frequency, type,
cflag);
// --snip--
int cominit(struct com_regs *regsp, int rate, int frequency, int
type, tcflag_t cflag)
{
if (bus_space_map(regsp->cr_iot, regsp->cr_iobase, regsp-
>cr_nports, 0, &regsp->cr_ioh))
int comcnattach(bus_space_tag_t iot, bus_addr_t iobase, int rate,
int frequency, int type, tcflag_t cflag)
{
// --snip--
regs.cr_iot = iot;
regs.cr_iobase = iobase;
regs.cr_nports = COM_NPORTS;
return comcnattach1(&regs, rate, frequency, type, cflag);
// --snip--
int comcnattach1(struct com_regs *regsp, int rate, int frequency,
int type, tcflag_t cflag)
{
// --snip--
comcons_info.regs = *regsp;
res = cominit(&comcons_info.regs, rate, frequency, type,
cflag);
// --snip--
int cominit(struct com_regs *regsp, int rate, int frequency, int
type, tcflag_t cflag)
{
if (bus_space_map(regsp->cr_iot, regsp->cr_iobase, regsp-
>cr_nports, 0, &regsp->cr_ioh))
int comcnattach(bus_space_tag_t iot, bus_addr_t iobase, int rate,
int frequency, int type, tcflag_t cflag)
{
// --snip--
regs.cr_iot = iot;
regs.cr_iobase = iobase;
regs.cr_nports = COM_NPORTS;
return comcnattach1(&regs, rate, frequency, type, cflag);
// --snip--
int comcnattach1(struct com_regs *regsp, int rate, int frequency,
int type, tcflag_t cflag)
{
// --snip--
comcons_info.regs = *regsp;
res = cominit(&comcons_info.regs, rate, frequency, type,
cflag);
// --snip--
int cominit(struct com_regs *regsp, int rate, int frequency, int
type, tcflag_t cflag)
{
if (bus_space_map(regsp->cr_iot, regsp->cr_iobase, regsp-
>cr_nports, 0, &regsp->cr_ioh))
int comcnattach(bus_space_tag_t iot, bus_addr_t iobase, int rate,
int frequency, int type, tcflag_t cflag)
{
// --snip--
regs.cr_iot = iot;
regs.cr_iobase = iobase;
regs.cr_nports = COM_NPORTS;
return comcnattach1(&regs, rate, frequency, type, cflag);
// --snip--
int comcnattach1(struct com_regs *regsp, int rate, int frequency,
int type, tcflag_t cflag)
{
// --snip--
comcons_info.regs = *regsp;
res = cominit(&comcons_info.regs, rate, frequency, type,
cflag);
// --snip--
int cominit(struct com_regs *regsp, int rate, int frequency, int
type, tcflag_t cflag)
{
if (bus_space_map(regsp->cr_iot, regsp->cr_iobase, regsp-
>cr_nports, 0, &regsp->cr_ioh))
int comcnattach(bus_space_tag_t iot, bus_addr_t iobase, int rate,
int frequency, int type, tcflag_t cflag)
{
// --snip--
regs.cr_iot = iot;
regs.cr_iobase = iobase;
regs.cr_nports = COM_NPORTS;
return comcnattach1(&regs, rate, frequency, type, cflag);
// --snip--
int comcnattach1(struct com_regs *regsp, int rate, int frequency,
int type, tcflag_t cflag)
{
// --snip--
comcons_info.regs = *regsp;
res = cominit(&comcons_info.regs, rate, frequency, type,
cflag);
// --snip--
int cominit(struct com_regs *regsp, int rate, int frequency, int
type, tcflag_t cflag)
{
if (bus_space_map(regsp->cr_iot, regsp->cr_iobase, regsp-
>cr_nports, 0, &regsp->cr_ioh))

17. comcnattach() callercomcnattach() callercomcnattach() callercomcnattach() callercomcnattach() caller
void
consinit(void)
{
// --snip--
#if (NCOM > 0)
if (!strcmp(consinfo->devname, "com")) {
int addr = consinfo->addr;
int speed = consinfo->speed;
if (addr == 0)
addr = CONADDR; // <= 0x3f8
if (speed == 0)
speed = CONSPEED;
if (comcnattach(x86_bus_space_io, addr, speed,
COM_FREQ, COM_TYPE_NORMAL,
comcnmode))
panic("can't init serial console @%x",
consinfo->addr);
return;
}
#endif
void
consinit(void)
{
// --snip--
#if (NCOM > 0)
if (!strcmp(consinfo->devname, "com")) {
int addr = consinfo->addr;
int speed = consinfo->speed;
if (addr == 0)
addr = CONADDR; // <= 0x3f8
if (speed == 0)
speed = CONSPEED;
if (comcnattach(x86_bus_space_io, addr, speed,
COM_FREQ, COM_TYPE_NORMAL,
comcnmode))
panic("can't init serial console @%x",
consinfo->addr);
return;
}
#endif
void
consinit(void)
{
// --snip--
#if (NCOM > 0)
if (!strcmp(consinfo->devname, "com")) {
int addr = consinfo->addr;
int speed = consinfo->speed;
if (addr == 0)
addr = CONADDR; // <= 0x3f8
if (speed == 0)
speed = CONSPEED;
if (comcnattach(x86_bus_space_io, addr, speed,
COM_FREQ, COM_TYPE_NORMAL,
comcnmode))
panic("can't init serial console @%x",
consinfo->addr);
return;
}
#endif
void
consinit(void)
{
// --snip--
#if (NCOM > 0)
if (!strcmp(consinfo->devname, "com")) {
int addr = consinfo->addr;
int speed = consinfo->speed;
if (addr == 0)
addr = CONADDR; // <= 0x3f8
if (speed == 0)
speed = CONSPEED;
if (comcnattach(x86_bus_space_io, addr, speed,
COM_FREQ, COM_TYPE_NORMAL,
comcnmode))
panic("can't init serial console @%x",
consinfo->addr);
return;
}
#endif
void
consinit(void)
{
// --snip--
#if (NCOM > 0)
if (!strcmp(consinfo->devname, "com")) {
int addr = consinfo->addr;
int speed = consinfo->speed;
if (addr == 0)
addr = CONADDR; // <= 0x3f8
if (speed == 0)
speed = CONSPEED;
if (comcnattach(x86_bus_space_io, addr, speed,
COM_FREQ, COM_TYPE_NORMAL,
comcnmode))
panic("can't init serial console @%x",
consinfo->addr);
return;
}
#endif

18. bus_space_map() (figure)bus_space_map() (figure)bus_space_map() (figure)bus_space_map() (figure)bus_space_map() (figure)