Re: [PATCH] sc16is7xx: Defer probe if device read fails

[Greg KH <gregkh@linuxfoundation.org>]

On Mon, Mar 29, 2021 at 03:40:35PM +0000, Annaliese McDermond wrote:
> A test was added to the probe function to ensure the device was
> actually connected and working before successfully completing a
> probe.  If the device was actually there, but the I2C bus was not
> ready yet for whatever reason, the probe fails permanently.
> 
> Change the probe so that we defer the probe on a regmap read
> failure so that we try the probe again when the dependent drivers
> are potentially loaded.  This should not affect the case where the
> device truly isn't present because the probe will never successfully
> complete.
> 
> Fixes: 2aa916e ("sc16is7xx: Read the LSR register for basic device presence check")

Please use the full 12 characters of the git commit id, as the
documentation asks for.  This should be:

Fixes: 2aa916e67db3 ("sc16is7xx: Read the LSR register for basic device presence check")

> Cc: stable@vger.kernel.org
> Signed-off-by: Annaliese McDermond <nh6z@nh6z.net>
> ---
>  drivers/tty/serial/sc16is7xx.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/tty/serial/sc16is7xx.c b/drivers/tty/serial/sc16is7xx.c
> index f86ec2d2635b..9adb8362578c 100644
> --- a/drivers/tty/serial/sc16is7xx.c
> +++ b/drivers/tty/serial/sc16is7xx.c
> @@ -1196,7 +1196,7 @@ static int sc16is7xx_probe(struct device *dev,
>  	ret = regmap_read(regmap,
>  			  SC16IS7XX_LSR_REG << SC16IS7XX_REG_SHIFT, &val);
>  	if (ret < 0)
> -		return ret;
> +		return -EPROBE_DEFER;
>  
>  	/* Alloc port structure */
>  	s = devm_kzalloc(dev, struct_size(s, p, devtype->nr_uart), GFP_KERNEL);
> -- 
> 2.27.0

Any reason you did not cc: the tty maintainer with this change?

thanks,

greg k-h