linux-kernel - Re: [RFC PATCH 2/2] driver core: add compatible string in sysfs for platform devices

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Date:   Wed, 3 Aug 2022 14:31:52 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Nipun Gupta <nipun.gupta@....com>
Cc:     linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        rafael@...nel.org, maz@...nel.org, tglx@...utronix.de,
        okaya@...nel.org, harpreet.anand@....com, michal.simek@....com,
        nikhil.agarwal@....com
Subject: Re: [RFC PATCH 2/2] driver core: add compatible string in sysfs for
 platform devices

On Wed, Aug 03, 2022 at 05:56:55PM +0530, Nipun Gupta wrote:
> For devices registered dynamically using platform_device_register
> API, this patch exposes the sysfs entry for the compatible string.
> 
> Signed-off-by: Nipun Gupta <nipun.gupta@....com>
> ---
>  drivers/base/platform.c | 15 +++++++++++++++
>  1 file changed, 15 insertions(+)
> 
> diff --git a/drivers/base/platform.c b/drivers/base/platform.c
> index 51bb2289865c..89949f88a0a1 100644
> --- a/drivers/base/platform.c
> +++ b/drivers/base/platform.c
> @@ -1289,10 +1289,25 @@ static ssize_t driver_override_store(struct device *dev,
>  }
>  static DEVICE_ATTR_RW(driver_override);
>  
> +static ssize_t compatible_show(struct device *dev, struct device_attribute *attr,
> +			      char *buf)
> +{
> +	const char *compat;
> +	int ret;
> +
> +	ret = device_property_read_string(dev, "compatible", &compat);
> +	if (ret != 0)
> +		return 0;
> +
> +	return sysfs_emit(buf, "%s", compat);
> +}
> +static DEVICE_ATTR_RO(compatible);

You forgot the Documentation/ABI/ update :(

Also, what happens if there is no such string to read?  Why are you
returning 0?  You should not create the attribute at all then, right?

thanks,

greg k-h