Re: [PATCH] ptp: ixp46x: Fix error handling in ptp_ixp_probe()

On Fri, Nov 26, 2021 at 2:40 AM tangbin [off-list ref] wrote:

On 2021/11/26 9:26, Linus Walleij wrote:

quoted

On Fri, Nov 26, 2021 at 2:10 AM Tang Bin [off-list ref] wrote:

quoted

In the function ptp_ixp_probe(), when get irq failed
after executing platform_get_irq(), the negative value
returned will not be detected here. So fix error handling
in this place.

Fixes: 9055a2f591629 ("ixp4xx_eth: make ptp support a platform driver")
Signed-off-by: Tang Bin <redacted>

OK the intention is right but:

quoted

-           !ixp_clock.master_irq || !ixp_clock.slave_irq)
+           (ixp_clock.master_irq < 0) || (ixp_clock.slave_irq < 0))

Keep disallowing 0. Because that is not a valid IRQ.

... <= 0 ...

Please look at the function platform_get_irq() in the file
drivers/base/platform.c,

the example is :

     * int irq = platform_get_irq(pdev, 0);

     * if (irq < 0)

     *        return irq;

In this case, reading the code is a bad idea. IRQ 0 is not valid,
and the fact that platform_get_irq() can return 0 does not make
it valid.

See:
https://lwn.net/Articles/470820/

Yours,
Linus Walleij