1. The document discusses device drivers in Linux, including file types, driver registration, hotplug, MMC size and partitions, and request queues and elevators. 2. It explains the process of an application opening a device file, how drivers are registered with the kernel, and how devices are handled when hotplugged. 3. Details are provided on how MMC sizes and partitions are represented, and how request queues and elevators are used to process I/O requests to block devices in an efficient manner.

1. 1
Chapter 6
Device Drivers

2. 2
● File Type
● From App to Device
● Driver Registration
● Hotplug
● MMC Size & Partitions
● Request Queue & Elevator

3. 3
File Type
*. 只有 type 為 b/c 的稱為 device file
*. type/major/minor 決定唯一 device
type major/minor
block device
mmc
可以存取任意位置
block
data 會被 cache 在 memory
b
沒特別意義
分區
character device
ir, uart
不行存取任意位置
byte
data 不被 cache 在 memory
c
類型 (e.g. memory)
子類型 (e.g. null/zero)
e.g.
data 存取
transfer unit
保留 data
type
白 major
白 minor

4. 4
From App to Device
vfs
執行預設 operations 裡的 open
1. 從 type 對應 table 根據 major/minor
找 driver 註冊的 cdev
2. 執行 cdev 自帶的 open( )
app
lib
syscall
filesystem
準備 inode &
安裝預設 operations
open device file
glibc/bionic
sys_open
do_sys_open
user space
kernel space
open( )
cdev

5. 5
From App to Device
user space
kernel space
.open
.llseek
.open
.llseek
.read
.write
.mmap
...
c device file
.open
.release
.llseek
.read
.write
.unlocked_ioctl
...
.open
.release
.ioctl
...
b device file
default
operations
driver
default
operations
driver
(partial)

6. 8
Driver Registration
1. 準備 cdev & operations
2. 註冊 region(major/minor)
(3. 註冊 hotplug 機制 , for probe)
1. 註冊 hotplug 機制 , for probe
----- probe 之後 -----
2. 準備 gendisk & operations &
request queue & elevator
3. 註冊 region(major/minor) &
add partition
open( )
read( )
write( )
cdev
0
1
254
cdev_map
open( )
read( )
write( )
cdev
open( )
read( )
write( )
cdev
0
1
254
bdev_map
open( )
read( )
write( )
gendisk
open( )
read( )
write( )
gendisk
request
queue
request
queue
elevator
elevator
minor minor
major major

7. 10
Hotplug
bus
usb
driver
mmc
driver
usb
device
sd
driver
match
fail
match
fail
match
pass
進行 probe
*. 這邊的 device, 是 kernel 內部自用的 struct
沒有 major/minor 概念

8. 11
Hotplug
bus
usb
driver
mmc
driver
usb
device
sd
driver
mmc
device
match
pass
進行 probe
1. 註冊 hotplug 機制 , for probe
----- probe 之後 -----
2. 準備 gendisk & operations &
request queue & elevator
3. 註冊 region(major/minor) &
add partition

9. 14
MMC Size & Partitions
partition
info
operations
gendisk
p0
noop
elevator
queue
request
queue
.request_fn
.make_request_fn
partition
table
1. 註冊 hotplug 機制 , for probe
----- probe 之後 -----
2. 準備 gendisk & operations &
request queue & elevator
3. 註冊 region(major/minor) &
add partition

10. 15
MMC Size & Partitions
sector
0
3
2
1
13
name = “MBOOT”
start_block = 4096
block_count = 6144
name = “RTPM”
start_block = 907264
block_count = 512
14 magic not match
name = “MPOOL”
start_block = 10240
block_count = 4096
MPOOL
MBOOT
partition table
KL
RFS
customer
MSLIB
APP
customerbackup
CONFIG
certificate
tee
RTPM
oad
7G
443M

11. 16
MMC Size & Partitions
noop
elevator
queue
request
queue
.request_fn
.make_request_fn
partition
table
partition
info
p1
partition
info
p2
partition
info
p13
.start_sect
.nr_sects
bdev
partition
info
operations
gendisk
p0
1. 註冊 hotplug 機制 , for probe
----- probe 之後 -----
2. 準備 gendisk & operations &
request queue & elevator
3. 註冊 region(major/minor) &
add partition
0
1
254
bdev_map
open( )
read( )
write( )
gendisk
open( )
read( )
write( )
gendisk
request
queue
request
queue
elevator
elevator

12. 22
Request Queue & Elevator
bio request
task plug
plug
elevator queue request queue
cfq usb disk A
deadline usb disk B
noop emmc

13. 23
Request Queue & Elevator
task plug
noop emmc
bio
plug
.make_request_fn: 把 bio 串入 plug/queue
.request_fn:
把 rq 從 request_queue 取出
交給 driver 處理 ( 先 drain)
.request_fn
.make_request_fn

14. 24
Request Queue & Elevator
task plug
noop emmc
bio
1. if plug
嘗試合併到 task plug 的 request
plug

15. 25
Request Queue & Elevator
task plug
noop emmc
bio
1. if plug
嘗試合併到 task plug 的 request
2. 嘗試合併到
elevator queue 的 requestplug

16. 26
Request Queue & Elevator
request
3. 包裝成 request
noop emmc
task plug
plug
elevator queue request queue

17. 27
Request Queue & Elevator
request
3. 包裝成 request
4. if plug, 串入 task plug
noop emmc
task plug
plug
elevator queue request queue

18. 28
Request Queue & Elevator
request
3. 包裝成 request
4. if plug, 串入 task plug
5. 串入 elevator queue
( 或 request queue)
執行 driver 處理 request queue
noop emmc
task plug
plug
elevator queue request queue

19. 29
Request Queue & Elevator
task plug
elevator queue request queue
cfq usb disk A
deadline usb disk B
noop emmc

20. 30
Request Queue & Elevator
task plug
elevator queue request queue
cfq usb disk A
deadline usb disk B
noop emmc
執行 driver
處理 request

21. 31
Request Queue & Elevator
task plug
elevator queue request queue
cfq usb disk A
deadline usb disk B
noop emmc
執行 driver
處理 request

22. 32
Request Queue & Elevator
task plug
elevator queue request queue
cfq usb disk A
deadline usb disk B
noop emmc
執行 driver
處理 request

23. 33
Request Queue & Elevator
request queue
page
frame
page
frame

24. 34
Request Queue & Elevator
request queue
mmc driver 把 request(read/write/...) 轉成 cmd 組合
page
frame
page
frame

25. 35
Request Queue & Elevator
request queue
mmc driver 把 request(read/write/...) 轉成 cmd 組合
敲 fcie register
透過 host 發送 protocol(cmd + data)
page
frame
page
frame
mstar fcie host
mstar fcie driver

26. 36
Request Queue & Elevator
request queue
mmc driver
mmc device
把 request(read/write/...) 轉成 cmd 組合
敲 fcie register
透過 host 發送 protocol(cmd + data)
根據收到 protocol 執行 cmd
達成 request(read/write/...)
read: storage --> dram
write: dram --> storage
其它 , flush/discard/write_same/zeroout/...
page
frame
page
frame
rw
rw
mstar fcie host
mstar fcie driver
cmddata