内核request_module学习不解之处
学习内核代码i2c过程中，driver/of/of_i2c.c中，of_i2c_register_devices的时候会调用到request_module("%s%s", I2C_MODULE_PREFIX, info.type);1,不理解这里为什么要调用request_module? --- 为了加载i2c设备驱动的ko吗？ 我看了我们的工程代码，I2C设备都是直接编译进内核的，不是ko。
2,关于request_module函数加载的模块名，相关资料显示是根据dts文件和一个叫modules.alias文件决定的。arch wiki上显示modules.alias文件路径为：/lib/modules/`uname -r`/modules.alias， 可是android系统不知道该文件的位置？
附上我找到的相关资料：
以下来自内核邮件列表：
If we are registering an i2c device that has a device tree node like
this real-world example:
rtc@68 {
compatible = "dallas,ds1337";
reg = <0x68>;
};
of_i2c_register_devices() will try to load a module called ds1337.ko.
There is no such module, so it will fail.If we look in modules.alias
we will find entries like these:
.
.
.
alias i2c:ds1339 rtc_ds1307
alias i2c:ds1338 rtc_ds1307
alias i2c:ds1337 rtc_ds1307
alias i2c:ds1307 rtc_ds1307
alias i2c:ds1374 rtc_ds1374
.
.
.
The module we want is really called rtc_ds1307.ko.If we request a
module called "i2c:ds1337", the userspace module loader will do the
right thing (unless it is busybox) and load rtc_ds1307.ko.So we add
the I2C_MODULE_PREFIX to the request_module() string.
Signed-off-by: David Daney <ddaney@caviumnetworks.com>
---
drivers/of/of_i2c.c | 2 +-
1 files changed, 1 insertions(+), 1 deletions(-)
diff --git a/drivers/of/of_i2c.c b/drivers/of/of_i2c.c
index c85d3c7..f37fbeb 100644
--- a/drivers/of/of_i2c.c
+++ b/drivers/of/of_i2c.c
@@ -61,7 +61,7 @@ void of_i2c_register_devices(struct i2c_adapter *adap)
info.of_node = of_node_get(node);
info.archdata = &dev_ad;
- request_module("%s", info.type);
+ request_module("%s%s", I2C_MODULE_PREFIX, info.type);
result = i2c_new_device(adap, &info);
if (result == NULL) {
--
1.7.2.3
---------------------------------
以下来自arch wiki：
so where is the modules.alias file?
grep snd_intel8x0m /lib/modules/`uname -r`/modules.alias
alias pci:v00008086d00002416sv*sd*bc*sc*i* snd_intel8x0m
alias pci:v00008086d00002426sv*sd*bc*sc*i* snd_intel8x0m
alias pci:v00008086d00002446sv*sd*bc*sc*i* snd_intel8x0m
alias pci:v00008086d00002486sv*sd*bc*sc*i* snd_intel8x0m
alias pci:v00008086d000024C6sv*sd*bc*sc*i* snd_intel8x0m
alias pci:v00008086d000024D6sv*sd*bc*sc*i* snd_intel8x0m
alias pci:v00008086d0000266Dsv*sd*bc*sc*i* snd_intel8x0m
alias pci:v00008086d000027DDsv*sd*bc*sc*i* snd_intel8x0m
alias pci:v00008086d00007196sv*sd*bc*sc*i* snd_intel8x0m
alias pci:v00001022d00007446sv*sd*bc*sc*i* snd_intel8x0m
alias pci:v00001039d00007013sv*sd*bc*sc*i* snd_intel8x0m
alias pci:v000010DEd000001C1sv*sd*bc*sc*i* snd_intel8x0m
alias pci:v000010DEd00000069sv*sd*bc*sc*i* snd_intel8x0m
alias pci:v000010DEd00000089sv*sd*bc*sc*i* snd_intel8x0m
alias pci:v000010DEd000000D9sv*sd*bc*sc*i* snd_intel8x0m
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