Subject: Re: [PATCH net-next] net: pse-pd: tps23881: Fix the device ID check

From: Thomas Petazzoni <[email-masked]>
Date: Tue, 30 Jul 2024 18:18:12 +0200

Hello Kyle,

On Tue, 30 Jul 2024 16:11:08 +0000
Kyle Swenson <[email-masked]> wrote:

> The DEVID register contains two pieces of information: the device ID in
> the upper nibble, and the silicon revision number in the lower nibble.
> The driver should work fine with any silicon revision, so let's mask
> that out in the device ID check.
> 
> Fixes: 20e6d190ffe1 ("net: pse-pd: Add TI TPS23881 PSE controller driver")
> Signed-off-by: Kyle Swenson <[email-masked]>
> ---
>  drivers/net/pse-pd/tps23881.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/net/pse-pd/tps23881.c b/drivers/net/pse-pd/tps23881.c
> index 61f6ad9c1934..bff8402fb382 100644
> --- a/drivers/net/pse-pd/tps23881.c
> +++ b/drivers/net/pse-pd/tps23881.c
> @@ -748,11 +748,11 @@ static int tps23881_i2c_probe(struct i2c_client *client)
>  
>  	ret = i2c_smbus_read_byte_data(client, TPS23881_REG_DEVID);
>  	if (ret < 0)
>  		return ret;
>  
> -	if (ret != 0x22) {
> +	if ((ret & 0xF0) != 0x20) {

Thanks for the patch! I believe it would make sense to use defines
here. At least for 0xF0, and perhaps for 0x20 as well.

Maybe:

#define TPS23881_REG_DEVID      		0x43
#define TPS23881_REG_DEVID_DEVID_MASK		0xF0
#define TPS23881_REG_DEVID_DEVID_VAL		0x2

and then:

	if (FIELD_GET(TPS23881_REG_DEVID_DEVID_MASK, ret) != 
            TPS23881_REG_DEVID_DEVID_VAL)

(totally untested, of course)

Best regards,

Thomas
-- 
Thomas Petazzoni, co-owner and CEO, Bootlin
Embedded Linux and Kernel engineering and training
https://bootlin.com