platform_driver_register() ??

platform_driver_register() ??

[Midhun Agnihotram]

Hi All,

  I have an MMC driver for my kit (i.MX21 based cogent board
CSB535FS), which is supplied by Cogent (Kernel version 2.6.16).

   The original driver (linux/drivers/mmc/mmc_block.c) uses
mmc_register_driver() method to register the driver but the one
supplied by Cogent uses platform_driver_register() method. What is the
difference between the two?


Thanks,
Midhun.

Re: platform_driver_register() ??

[Nobin Mathew]

Hi Midhun,
    I think mmc driver is layered modules, only top block driver
registers driver under  "mmc_bus_type" bus, see
drivers/mmc/mmc_sysfs.c and mmc_block.c. I think they are creating a
tree of devices of same characteristics under that bus.
I think your driver is linux/drivers/mmc/imxmmc.c where it registers a
driver for device of type "platform_bus_type". This module will come
under above mentioned block driver.
Corresponding platform device is registered in
linux/arch/arm/mach-imx/generic.c see platform_device imx_mmc_device.

Nobin Mathew




On 7/3/07, Midhun Agnihotram <agnimidhun@gmail.com> wrote:
> Hi All,
>
>  I have an MMC driver for my kit (i.MX21 based cogent board
> CSB535FS), which is supplied by Cogent (Kernel version 2.6.16).
>
>   The original driver (linux/drivers/mmc/mmc_block.c) uses
> mmc_register_driver() method to register the driver but the one
> supplied by Cogent uses platform_driver_register() method. What is the
> difference between the two?
>
>
> Thanks,
> Midhun.
> -
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Re: platform_driver_register() ??

[Pierre Ossman]

On Tue, 3 Jul 2007 18:28:40 +0530
"Nobin Mathew" <nobin.mathew@gmail.com> wrote:

> Hi Midhun,
>     I think mmc driver is layered modules, only top block driver
> registers driver under  "mmc_bus_type" bus, see
> drivers/mmc/mmc_sysfs.c and mmc_block.c. I think they are creating a
> tree of devices of same characteristics under that bus.
> I think your driver is linux/drivers/mmc/imxmmc.c where it registers a
> driver for device of type "platform_bus_type". This module will come
> under above mentioned block driver.
> Corresponding platform device is registered in
> linux/arch/arm/mach-imx/generic.c see platform_device imx_mmc_device.
> 

Indeed. You seem to have the hang of this ;)

Rgds
-- 
     -- Pierre Ossman

  Linux kernel, MMC maintainer        http://www.kernel.org
  PulseAudio, core developer          http://pulseaudio.org
  rdesktop, core developer          http://www.rdesktop.org

Re: platform_driver_register() ??

[Midhun Agnihotram]

Hi All,


> >     I think mmc driver is layered modules, only top block driver
> > registers driver under  "mmc_bus_type" bus, see
> > drivers/mmc/mmc_sysfs.c and mmc_block.c. I think they are creating a
> > tree of devices of same characteristics under that bus.
> > I think your driver is linux/drivers/mmc/imxmmc.c where it registers a
> > driver for device of type "platform_bus_type". This module will come
> > under above mentioned block driver.
> > Corresponding platform device is registered in
> > linux/arch/arm/mach-imx/generic.c see platform_device imx_mmc_device.


    Is it necessary that the firmware (may be bootloader) notify about
the MMC host to Linux? The kernel documentation (platform.txt) says :

 "The firmware should notify the platform bus about devices before the
legacy drivers have had a chance to load."

   Have I interpreted the above sentence correctly?

Thanks,
Midhun.

Re: platform_driver_register() ??

[Pierre Ossman]

On Thu, 5 Jul 2007 14:51:35 +0530
"Midhun Agnihotram" <agnimidhun@gmail.com> wrote:

> 
>     Is it necessary that the firmware (may be bootloader) notify about
> the MMC host to Linux? The kernel documentation (platform.txt) says :
> 
>  "The firmware should notify the platform bus about devices before the
> legacy drivers have had a chance to load."
> 
>    Have I interpreted the above sentence correctly?
> 

I don't know what the meaning of that sentence was supposed to be, but
platform devices are everything the kernel cannot probe in a "normal"
way. Usually this covers devices that cannot be probed at all, but must
be listed some other way (i.e. manually).

Commonly the arch and machine specific code adds the devices. The
machine code is usually specific to a certain hardware, so the code
"knows" which devices are present, even though it can't probe them.

So to answer your question; no, the firmware doesn't have to tell Linux
about the devices.

Rgds
-- 
     -- Pierre Ossman

  Linux kernel, MMC maintainer        http://www.kernel.org
  PulseAudio, core developer          http://pulseaudio.org
  rdesktop, core developer          http://www.rdesktop.org