Re: [PATCH] drm/msm/dsi: fix error checks and return values for DSI xmit functions

[Abhinav Kumar <quic_abhinavk@quicinc.com>]

On 4/1/2022 4:11 PM, Dmitry Baryshkov wrote:
> As noticed by Dan ([1] an the followup thread) there are multiple issues
> with the return values for MSM DSI command transmission callback. In
> the error case it can easily return a positive value when it should
> have returned a proper error code.
> 
> This commits attempts to fix these issues both in TX and in RX paths.
> 
> [1]: https://lore.kernel.org/linux-arm-msm/20211001123617.GH2283@kili/
> 
> Fixes: a689554ba6ed ("drm/msm: Initial add DSI connector support")
> Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
> Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>

Looks reasonable to me,

Reviewed-by: Abhinav Kumar <quic_abhinavk@quicinc.com>

> ---
>   drivers/gpu/drm/msm/dsi/dsi_host.c | 21 ++++++++++++++-------
>   1 file changed, 14 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/gpu/drm/msm/dsi/dsi_host.c b/drivers/gpu/drm/msm/dsi/dsi_host.c
> index d51e70fab93d..8925f60fd9ec 100644
> --- a/drivers/gpu/drm/msm/dsi/dsi_host.c
> +++ b/drivers/gpu/drm/msm/dsi/dsi_host.c
> @@ -1341,10 +1341,10 @@ static int dsi_cmds2buf_tx(struct msm_dsi_host *msm_host,
>   			dsi_get_bpp(msm_host->format) / 8;
>   
>   	len = dsi_cmd_dma_add(msm_host, msg);
> -	if (!len) {
> +	if (len < 0) {
>   		pr_err("%s: failed to add cmd type = 0x%x\n",
>   			__func__,  msg->type);
> -		return -EINVAL;
> +		return len;
>   	}
>   
>   	/* for video mode, do not send cmds more than
> @@ -1363,10 +1363,14 @@ static int dsi_cmds2buf_tx(struct msm_dsi_host *msm_host,
>   	}
>   
>   	ret = dsi_cmd_dma_tx(msm_host, len);
> -	if (ret < len) {
> -		pr_err("%s: cmd dma tx failed, type=0x%x, data0=0x%x, len=%d\n",
> -			__func__, msg->type, (*(u8 *)(msg->tx_buf)), len);
> -		return -ECOMM;
> +	if (ret < 0) {
> +		pr_err("%s: cmd dma tx failed, type=0x%x, data0=0x%x, len=%d, ret=%d\n",
> +			__func__, msg->type, (*(u8 *)(msg->tx_buf)), len, ret);
> +		return ret;
> +	} else if (ret < len) {
> +		pr_err("%s: cmd dma tx failed, type=0x%x, data0=0x%x, ret=%d len=%d\n",
> +			__func__, msg->type, (*(u8 *)(msg->tx_buf)), ret, len);
> +		return -EIO;
>   	}
>   
>   	return len;
> @@ -2092,9 +2096,12 @@ int msm_dsi_host_cmd_rx(struct mipi_dsi_host *host,
>   		}
>   
>   		ret = dsi_cmds2buf_tx(msm_host, msg);
> -		if (ret < msg->tx_len) {
> +		if (ret < 0) {
>   			pr_err("%s: Read cmd Tx failed, %d\n", __func__, ret);
>   			return ret;
> +		} else if (ret < msg->tx_len) {
> +			pr_err("%s: Read cmd Tx failed, too short: %d\n", __func__, ret);
> +			return -ECOMM;
>   		}
>   
>   		/*