Re: [PATCH 22/22] usb: host: xhci-tegra: deny IRQ0

[Dmitry Osipenko <digetx@gmail.com>]

26.10.2021 21:24, Sergey Shtylyov пишет:
> Hello!
> 
> On 10/21/21 12:09 PM, Dmitry Osipenko wrote:
> [...]
>>> If platform_get_irq() returns IRQ0 (considered invalid according to Linus)
>>> the driver blithely passes it to usb_add_hcd() that treats IRQ0 as no IRQ
>>> at all. Deny IRQ0 right away, returning -EINVAL from the probe() method...
>>>
>>> Fixes: e84fce0f8837 ("usb: xhci: Add NVIDIA Tegra XUSB controller driver")
>>> Signed-off-by: Sergey Shtylyov <s.shtylyov@omp.ru>
>>> ---
>>>  drivers/usb/host/xhci-tegra.c | 2 ++
>>>  1 file changed, 2 insertions(+)
>>>
>>> diff --git a/drivers/usb/host/xhci-tegra.c b/drivers/usb/host/xhci-tegra.c
>>> index 1bf494b649bd..7151b1d4f876 100644
>>> --- a/drivers/usb/host/xhci-tegra.c
>>> +++ b/drivers/usb/host/xhci-tegra.c
>>> @@ -1439,6 +1439,8 @@ static int tegra_xusb_probe(struct platform_device *pdev)
>>>  	tegra->xhci_irq = platform_get_irq(pdev, 0);
>>>  	if (tegra->xhci_irq < 0)
>>>  		return tegra->xhci_irq;
>>> +	if (!tegra->xhci_irq)
>>> +		return -ENIVAL;
>>>  
>>>  	tegra->mbox_irq = platform_get_irq(pdev, 1);
>>>  	if (tegra->mbox_irq < 0)
>>>
>>
>> platform_get_irq() never returns zero in accordance to [1], but I see
>> that it can return it [2].
> 
>    Not only that, it also can be returned thru the normal path (from an IRQ descriptor).
> I'm not sure whether 0 means an IRQ0 returned from acpi_dev_gpio_irq_get(), looks like yes...
> 
>> Should be better to fix [2] and return -EINVAL.
> 
>    No, we have WARN() before returning IRQ0 -- if we're going to finally declare IRQ0 invalid,
> it should be done after this check.

Warning is already explicitly saying that IRQ0 is invalid, hence IRQ0
*is* declared invalid. Either doc comment or function itself is wrong,
both are bad.

If function is wrong, then you're fixing symptom instead of fixing the
root of the problem.