[PATCH] drm/panel/raspberrypi-touchscreen: Fix error handling in rpi_touchscreen_init()

[Yuan Can]

在 2022/11/14 19:55, Dave Stevenson 写道:
> Hi Yuan
>
> On Mon, 14 Nov 2022 at 08:21, Yuan Can <yuancan at huawei.com> wrote:
>> A problem about modprobe panel-raspberrypi-touchscreen is triggered with
>> the following log given:
>>
>>   [  542.980748] Error: Driver 'rpi-ts-dsi' is already registered, aborting...
>>
>> And with this log printed, the panel_raspberrypi_touchscreen is listed by
>> lsmod, rmmod on it can trigger the WARN of "Unexpected driver unregister".
>>
>> The reason is that the return value of mipi_dsi_driver_register() and
>> i2c_add_driver() is not checked in rpi_touchscreen_init(), if
>> i2c_add_driver() failed, the rpi_touchscreen_dsi_driver is never
>> unregistered, and next time when install this module, the
>> mipi_dsi_driver_register() is failed but rpi_touchscreen_init() returns 0,
>> leading to the panel_raspberrypi_touchscreen listed by lsmod.
>>
>> Call graph of modprobe panel-raspberrypi-touchscreen at the first time:
>>   rpi_touchscreen_init()
>>     mipi_dsi_driver_register() # register rpi_touchscreen_dsi_driver
>>     i2c_add_driver()
>>       driver_register()
>>         bus_add_driver()
>>           priv = kzalloc(...) # OOM happened
>>   # return without unregister rpi_touchscreen_dsi_driver
>>
>> Call graph of retrying modprobe panel-raspberrypi-touchscreen:
>>   rpi_touchscreen_init()
>>     mipi_dsi_driver_register() # Error message printed, register failed!
>>     i2c_add_driver() # succeed and return
>>
>> Fix by checking the return value of both functions and unregister
>> rpi_touchscreen_dsi_driver if i2c_add_driver() failed.
>>
>> Fixes: 2f733d6194bd ("drm/panel: Add support for the Raspberry Pi 7" Touchscreen.")
>> Signed-off-by: Yuan Can <yuancan at huawei.com>
> Acked-by: Dave Stevenson <dave.stevenson at raspberrypi.com>
>
> I would strongly recommend that you look at switching to the tc358762
> bridge, panel-simple, and the rpi-panel-attiny-regulator regulator
> driver, rather than this driver.
>
> The raspberrypi-touchscreen driver has no suitable hooks for the
> edt-ft5x06 touch driver to register for regulator control. If the
> display sleeps then the power is killed to the touch controller but
> the touch driver has no knowledge of this. This issue should have been
> solved with rpi-panel-attiny / tc358762 / panel-simple.
Thanks for the suggestion!

-- 
Best regards,
Yuan Can