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Subject: Re: [PATCH] drm/dsi: Fix improper use of mipi_dsi_device_transfer()
 return value
To: Philippe Cornu <philippe.cornu@st.com>,
        Daniel Vetter <daniel.vetter@intel.com>,
        Gustavo Padovan <gustavo@padovan.org>,
        Sean Paul <seanpaul@chromium.org>,
        David Airlie <airlied@linux.ie>,
        dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org
Cc: Archit Taneja <architt@codeaurora.org>,
        Brian Norris <briannorris@chromium.org>,
        Benjamin Gaignard <benjamin.gaignard@linaro.org>,
        Yannick Fertre <yannick.fertre@st.com>,
        Vincent Abriou <vincent.abriou@st.com>,
        Alexandre Torgue <alexandre.torgue@st.com>
From: Andrzej Hajda <a.hajda@samsung.com>
Message-id: <e3936ab6-742a-de54-1d43-510134c3fe65@samsung.com>
Date: Mon, 15 Jan 2018 10:12:24 +0100
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References: <CGME20180112144953epcas2p3046bd1b5cb6de9a616c5e6688cee97b4@epcas2p3.samsung.com>
        <20180112144847.18810-1-philippe.cornu@st.com>
Sender: linux-kernel-owner@vger.kernel.org

On 12.01.2018 15:48, Philippe Cornu wrote:
> The function mipi_dsi_device_transfer() returns the number of transmitted
> or received bytes on success or a negative error code on failure.
>
> The functions mipi_dsi_shutdown_peripheral(), mipi_dsi_turn_on_peripheral() &
> mipi_dsi_set_maximum_return_packet_size() use improperly this returned
> value in case of success: 0 should be returned instead of the number of
> transmitted bytes.
>
> Signed-off-by: Philippe Cornu <philippe.cornu@st.com>

I guess, the best would be to create and use some helper similar to
PTR_ERR_OR_ZERO,
but this is also OK.

Reviewed-by: Andrzej Hajda <a.hajda@samsung.com>

 --
Regards
Andrzej

> ---
>  drivers/gpu/drm/drm_mipi_dsi.c | 9 ++++++---
>  1 file changed, 6 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_mipi_dsi.c b/drivers/gpu/drm/drm_mipi_dsi.c
> index 4b47226b90d4..bc73b7f5b9fc 100644
> --- a/drivers/gpu/drm/drm_mipi_dsi.c
> +++ b/drivers/gpu/drm/drm_mipi_dsi.c
> @@ -498,8 +498,9 @@ int mipi_dsi_shutdown_peripheral(struct mipi_dsi_device *dsi)
>  		.tx_buf = (u8 [2]) { 0, 0 },
>  		.tx_len = 2,
>  	};
> +	int ret = mipi_dsi_device_transfer(dsi, &msg);
>  
> -	return mipi_dsi_device_transfer(dsi, &msg);
> +	return (ret < 0) ? ret : 0;
>  }
>  EXPORT_SYMBOL(mipi_dsi_shutdown_peripheral);
>  
> @@ -517,8 +518,9 @@ int mipi_dsi_turn_on_peripheral(struct mipi_dsi_device *dsi)
>  		.tx_buf = (u8 [2]) { 0, 0 },
>  		.tx_len = 2,
>  	};
> +	int ret = mipi_dsi_device_transfer(dsi, &msg);
>  
> -	return mipi_dsi_device_transfer(dsi, &msg);
> +	return (ret < 0) ? ret : 0;
>  }
>  EXPORT_SYMBOL(mipi_dsi_turn_on_peripheral);
>  
> @@ -541,8 +543,9 @@ int mipi_dsi_set_maximum_return_packet_size(struct mipi_dsi_device *dsi,
>  		.tx_len = sizeof(tx),
>  		.tx_buf = tx,
>  	};
> +	int ret = mipi_dsi_device_transfer(dsi, &msg);
>  
> -	return mipi_dsi_device_transfer(dsi, &msg);
> +	return (ret < 0) ? ret : 0;
>  }
>  EXPORT_SYMBOL(mipi_dsi_set_maximum_return_packet_size);
>