linux-kernel - Re: [PATCH v2] mfd: cros_ec_dev: Return number of bytes read with CROS_EC_DEV

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Message-ID: <20190206192623.GA120245@google.com>
Date:   Wed, 6 Feb 2019 11:26:23 -0800
From:   Benson Leung <bleung@...gle.com>
To:     Enric Balletbo i Serra <enric.balletbo@...labora.com>
Cc:     linux-kernel@...r.kernel.org, groeck@...omium.org,
        lee.jones@...aro.org, gwendal@...omium.org, kernel@...labora.com,
        bleung@...omium.org, Guenter Roeck <linux@...ck-us.net>,
        bleung@...gle.com
Subject: Re: [PATCH v2] mfd: cros_ec_dev: Return number of bytes read with
 CROS_EC_DEV_IOCRDMEM

On Wed, Feb 06, 2019 at 06:39:59PM +0100, Enric Balletbo i Serra wrote:
> From: Guenter Roeck <linux@...ck-us.net>
> 
> While ioctls normally return a negative error or 0 on success, this is not
> the case for CROS_EC_DEV_IOCXCMD in the cros_ec driver, which returns the
> number of bytes read instead. However, CROS_EC_DEV_IOCRDMEM in the same
> driver does not return the number of byte read on success. This is both
> inconsistent and problematic, since the amount of returned data can be
> dynamic. Have it return the number of data bytes for consistency.
> 
> Signed-off-by: Guenter Roeck <linux@...ck-us.net>
> Signed-off-by: Enric Balletbo i Serra <enric.balletbo@...labora.com>

Reviewed-by: Benson Leung <bleung@...omium.org>

> ---
> Hi,
> 
> This patch was send long time ago and never landed to mainline [1]. This
> is a second attempt. Originally was made to apply on platform/chrome but
> after the recent changes we did it should go now throught the MFD
> subsystem. Without this patch userspace tools like ectool doesn't work
> as expected.
> 
> Best regards,
>  Enric
> 
> [1] https://lore.kernel.org/patchwork/patch/665211/
> 
> Changes in v2:
> - Adapt and rebase to current mainline.
> 
>  drivers/mfd/cros_ec_dev.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/mfd/cros_ec_dev.c b/drivers/mfd/cros_ec_dev.c
> index ed809fc97df8..d275deaecb12 100644
> --- a/drivers/mfd/cros_ec_dev.c
> +++ b/drivers/mfd/cros_ec_dev.c
> @@ -224,7 +224,7 @@ static long ec_device_ioctl_readmem(struct cros_ec_dev *ec, void __user *arg)
>  	if (copy_to_user((void __user *)arg, &s_mem, sizeof(s_mem)))
>  		return -EFAULT;
>  
> -	return 0;
> +	return num;
>  }
>  
>  static long ec_device_ioctl(struct file *filp, unsigned int cmd,
> -- 
> 2.20.1
> 

-- 
Benson Leung
Staff Software Engineer
Chrome OS Kernel
Google Inc.
bleung@...gle.com
Chromium OS Project
bleung@...omium.org

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