linux-kernel - Re: [PATCH] drm/bridge: analogix_dp: Don't return -EBUSY when msg->size is 0 in aux transaction

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Date:   Mon, 20 Feb 2017 10:13:42 +0800
From:   Zain Wang <wzz@...k-chips.com>
To:     Sean Paul <seanpaul@...omium.org>,
        Daniel Vetter <daniel.vetter@...ll.ch>,
        Inki Dae <inki.dae@...sung.com>,
        David Airlie <airlied@...ux.ie>
Cc:     Tomeu Vizoso <tomeu.vizoso@...labora.com>,
        Mika Kahola <mika.kahola@...el.com>,
        Stéphane Marchesin <marcheu@...omium.org>,
        Tomasz Figa <tfiga@...omium.org>, dianders@...omium.org,
        Thierry Reding <treding@...dia.com>,
        Heiko Stuebner <heiko@...ech.de>,
        Jingoo Han <jingoohan1@...il.com>,
        Javier Martinez Canillas <javier@....samsung.com>,
        linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        linux-samsung-soc@...r.kernel.org,
        linux-rockchip@...ts.infradead.org
Subject: Re: [PATCH] drm/bridge: analogix_dp: Don't return -EBUSY when
 msg->size is 0 in aux transaction

Hi Sean,

     Could you give some comments for this patch?

Thanks
Zain


在 2017/2/13 17:27, zain wang 写道:
> The analogix_dp_transfer() will return -EBUSY if num_transferred is zero.
> But sometimes we will send a bare address packet to start the transaction,
> like drm_dp_i2c_xfer() show:
> 	......
> 	/* Send a bare address packet to start the transaction.
> 	 * Zero sized messages specify an address only (bare
> 	 * address) transaction.
> 	 */
> 	msg.buffer = NULL;
> 	msg.size = 0;
> 	err = drm_dp_i2c_do_msg(aux, &msg);
> 	......
>
> In this case, the msg->size is zero, so the num_transferred will be zero too.
> We can't return -EBUSY here, let's we return num_transferred if num_transferred
> equals msg->size.
>
> Signed-off-by: zain wang <wzz@...k-chips.com>
> ---
>   drivers/gpu/drm/bridge/analogix/analogix_dp_reg.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/bridge/analogix/analogix_dp_reg.c b/drivers/gpu/drm/bridge/analogix/analogix_dp_reg.c
> index 303083a..5384aca 100644
> --- a/drivers/gpu/drm/bridge/analogix/analogix_dp_reg.c
> +++ b/drivers/gpu/drm/bridge/analogix/analogix_dp_reg.c
> @@ -1162,5 +1162,5 @@ ssize_t analogix_dp_transfer(struct analogix_dp_device *dp,
>   		 (msg->request & ~DP_AUX_I2C_MOT) == DP_AUX_NATIVE_READ)
>   		msg->reply = DP_AUX_NATIVE_REPLY_ACK;
>   
> -	return num_transferred > 0 ? num_transferred : -EBUSY;
> +	return (num_transferred == msg->size) ? num_transferred : -EBUSY;
>   }