On 7 September 2016 at 19:53, Romain Perier
<romain.perier@xxxxxxxxxxxxxxxxxx> wrote:
> Hello,
>
>
> Le 06/09/2016 18:31, PrasannaKumar Muralidharan a écrit :
>>>
>>> Use devm_hwrng_register instead of hwrng_register. It avoids the need
>>> to handle unregistration explicitly from the remove function.
>>>
>>> Signed-off-by: Romain Perier <romain.perier@xxxxxxxxxxxxxxxxxx>
>>> ---
>>> drivers/char/hw_random/omap-rng.c | 4 +---
>>> 1 file changed, 1 insertion(+), 3 deletions(-)
>>>
>>> diff --git a/drivers/char/hw_random/omap-rng.c
>>> b/drivers/char/hw_random/omap-rng.c
>>> index d47b24d..171c3e8 100644
>>> --- a/drivers/char/hw_random/omap-rng.c
>>> +++ b/drivers/char/hw_random/omap-rng.c
>>> @@ -381,7 +381,7 @@ static int omap_rng_probe(struct platform_device
>>> *pdev)
>>> if (ret)
>>> goto err_ioremap;
>>>
>>> - ret = hwrng_register(&omap_rng_ops);
>>> + ret = devm_hwrng_register(dev, &omap_rng_ops);
>>> if (ret)
>>> goto err_register;
>>>
>>> @@ -402,8 +402,6 @@ static int omap_rng_remove(struct platform_device
>>> *pdev)
>>> {
>>> struct omap_rng_dev *priv = platform_get_drvdata(pdev);
>>>
>>> - hwrng_unregister(&omap_rng_ops);
>>> -
>>> priv->pdata->cleanup(priv);
>>>
>>> pm_runtime_put_sync(&pdev->dev);
>>> --
>>
>>
>> If devm_hwrng_register is used hwrng_unregister will be called after
>> pm_runtime_disable is called. If RNG device is in use calling
>> omap_rng_remove may not work properly.
>>
>
> The case where the remove function is called is if you unbind the driver by
> hand or you call rmmod while the RNG device is used.
> I don't think that the kernel will call platform->remove is the device is in
> use (so /dev/hwrng). I mean the argument that the unregister function is
> called after pm_runtime_disable is correct, but I don't think that the
> remove function might be called while the device is in use. There is
> necessarily a mutual exclusive case between "use the device" and "call the
> remove function of the device". However, I am open to suggestions.
The way you explained is good :D. Good point too. But the device is
created by hw_random core (hwrng_modinit in core.c) so the device can
be in use when omap-rng module is removed. Please feel free to correct
me if I am wrong.
Cheers,
PrasannaKumar
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