Re: [PATCH v2 1/5] platform/chrome: cros_ec_lpc: MEC access can return error code

[Tzung-Bi Shih <tzungbi@kernel.org>]

On Mon, Jun 03, 2024 at 07:38:30AM +0100, Ben Walsh wrote:
> @@ -425,8 +469,8 @@ static int cros_ec_lpc_probe(struct platform_device *pdev)
>  	 */
>  	cros_ec_lpc_ops.read = cros_ec_lpc_mec_read_bytes;
>  	cros_ec_lpc_ops.write = cros_ec_lpc_mec_write_bytes;
> -	cros_ec_lpc_ops.read(EC_LPC_ADDR_MEMMAP + EC_MEMMAP_ID, 2, buf);
> -	if (buf[0] != 'E' || buf[1] != 'C') {
> +	ret = cros_ec_lpc_ops.read(EC_LPC_ADDR_MEMMAP + EC_MEMMAP_ID, 2, buf);
> +	if (ret < 0 || buf[0] != 'E' || buf[1] != 'C') {

Slight concern: if the read failed (-EBUSY, because of the lock contention
failed for example), does it still need to probe for non-MEC devices?

> @@ -436,9 +480,9 @@ static int cros_ec_lpc_probe(struct platform_device *pdev)
>  		/* Re-assign read/write operations for the non MEC variant */
>  		cros_ec_lpc_ops.read = cros_ec_lpc_read_bytes;
>  		cros_ec_lpc_ops.write = cros_ec_lpc_write_bytes;
> -		cros_ec_lpc_ops.read(ec_lpc->mmio_memory_base + EC_MEMMAP_ID, 2,
> -				     buf);
> -		if (buf[0] != 'E' || buf[1] != 'C') {
> +		ret = cros_ec_lpc_ops.read(ec_lpc->mmio_memory_base + EC_MEMMAP_ID, 2,
> +					   buf);
> +		if (ret < 0 || buf[0] != 'E' || buf[1] != 'C') {
>  			dev_err(dev, "EC ID not detected\n");
>  			return -ENODEV;

Similar concern here: should `ret < 0` see as a -ENODEV?