Re: [PATCH 3/4] drm/dsi: Make mipi_dsi_dcs_{read, write}() symmetrical

[Andrzej Hajda <a.hajda@samsung.com>]

On 07/22/2014 01:20 PM, Daniel Vetter wrote:
> On Tue, Jul 22, 2014 at 09:12:20AM +0200, Thierry Reding wrote:
>> From: Thierry Reding <treding@nvidia.com>
>>
>> Currently the mipi_dsi_dcs_write() function requires the DCS command
>> byte to be embedded within the write buffer whereas mipi_dsi_dcs_read()
>> has a separate parameter. Make them more symmetrical by adding an extra
>> command parameter to mipi_dsi_dcs_write().
>>
>> Also update the S6E8AA0 panel driver (the only user of this API) to
>> adapt to this new API.
>>
>> Signed-off-by: Thierry Reding <treding@nvidia.com>
> Given the patterns established by other sideband subsystesm like i2c or
> the dp aux helpers we have in drm I think this is going into the right
> direction. Also, this seems to match somewhat the style we have in our
> hand-rolled intel dsi implementation. So I think this makes sense.

Could you point me out the patterns you are referring to.

Regarding intel dsi implementation I have found in intel_dsi_cmd.h:

    int dsi_vc_dcs_write(struct intel_dsi *intel_dsi, int channel,
        const u8 *data, int len);
    int dsi_vc_dcs_read(struct intel_dsi *intel_dsi, int channel,
        u8 dcs_cmd, u8 *buf, int buflen);

This is the same approach as in the current drm mipi, no forced symmetry.

There are also helpers for simple DCS commands: dsi_vc_dcs_write_[01],
but they
are using dsi_vc_dcs_write internally, which seems to me more reasonable.

Regards
Andrzej

>
> Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
>> ---
>>  drivers/gpu/drm/drm_mipi_dsi.c        | 45 ++++++++++++++++++++++++-----------
>>  drivers/gpu/drm/panel/panel-s6e8aa0.c |  4 ++--
>>  include/drm/drm_mipi_dsi.h            |  4 ++--
>>  3 files changed, 35 insertions(+), 18 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/drm_mipi_dsi.c b/drivers/gpu/drm/drm_mipi_dsi.c
>> index 6aa6a9e95570..bbab06ef80c9 100644
>> --- a/drivers/gpu/drm/drm_mipi_dsi.c
>> +++ b/drivers/gpu/drm/drm_mipi_dsi.c
>> @@ -201,29 +201,41 @@ EXPORT_SYMBOL(mipi_dsi_detach);
>>  /**
>>   * mipi_dsi_dcs_write - send DCS write command
>>   * @dsi: DSI device
>> - * @data: pointer to the command followed by parameters
>> - * @len: length of @data
>> + * @cmd: DCS command
>> + * @data: pointer to the command payload
>> + * @len: payload length
>>   */
>> -ssize_t mipi_dsi_dcs_write(struct mipi_dsi_device *dsi, const void *data,
>> -			    size_t len)
>> +ssize_t mipi_dsi_dcs_write(struct mipi_dsi_device *dsi, u8 cmd,
>> +			   const void *data, size_t len)
>>  {
>>  	const struct mipi_dsi_host_ops *ops = dsi->host->ops;
>> -	struct mipi_dsi_msg msg = {
>> -		.channel = dsi->channel,
>> -		.tx_buf = data,
>> -		.tx_len = len
>> -	};
>> +	struct mipi_dsi_msg msg;
>> +	ssize_t err;
>> +	u8 *tx;
>>  
>>  	if (!ops || !ops->transfer)
>>  		return -ENOSYS;
>>  
>> +	if (len > 0) {
>> +		tx = kmalloc(1 + len, GFP_KERNEL);
>> +		if (!tx)
>> +			return -ENOMEM;
>> +
>> +		tx[0] = cmd;
>> +		memcpy(tx + 1, data, len);
>> +	} else {
>> +		tx = &cmd;
>> +	}
>> +
>> +	msg.channel = dsi->channel;
>> +	msg.tx_len = 1 + len;
>> +	msg.tx_buf = tx;
>> +
>>  	switch (len) {
>>  	case 0:
>> -		return -EINVAL;
>> -	case 1:
>>  		msg.type = MIPI_DSI_DCS_SHORT_WRITE;
>>  		break;
>> -	case 2:
>> +	case 1:
>>  		msg.type = MIPI_DSI_DCS_SHORT_WRITE_PARAM;
>>  		break;
>>  	default:
>> @@ -231,14 +243,19 @@ ssize_t mipi_dsi_dcs_write(struct mipi_dsi_device *dsi, const void *data,
>>  		break;
>>  	}
>>  
>> -	return ops->transfer(dsi->host, &msg);
>> +	err = ops->transfer(dsi->host, &msg);
>> +
>> +	if (len > 0)
>> +		kfree(tx);
>> +
>> +	return err;
>>  }
>>  EXPORT_SYMBOL(mipi_dsi_dcs_write);
>>  
>>  /**
>>   * mipi_dsi_dcs_read - send DCS read request command
>>   * @dsi: DSI device
>> - * @cmd: DCS read command
>> + * @cmd: DCS command
>>   * @data: pointer to read buffer
>>   * @len: length of @data
>>   *
>> diff --git a/drivers/gpu/drm/panel/panel-s6e8aa0.c b/drivers/gpu/drm/panel/panel-s6e8aa0.c
>> index 5502ef6bc074..d39bee36816c 100644
>> --- a/drivers/gpu/drm/panel/panel-s6e8aa0.c
>> +++ b/drivers/gpu/drm/panel/panel-s6e8aa0.c
>> @@ -130,7 +130,7 @@ static int s6e8aa0_clear_error(struct s6e8aa0 *ctx)
>>  	return ret;
>>  }
>>  
>> -static void s6e8aa0_dcs_write(struct s6e8aa0 *ctx, const void *data, size_t len)
>> +static void s6e8aa0_dcs_write(struct s6e8aa0 *ctx, const u8 *data, size_t len)
>>  {
>>  	struct mipi_dsi_device *dsi = to_mipi_dsi_device(ctx->dev);
>>  	ssize_t ret;
>> @@ -138,7 +138,7 @@ static void s6e8aa0_dcs_write(struct s6e8aa0 *ctx, const void *data, size_t len)
>>  	if (ctx->error < 0)
>>  		return;
>>  
>> -	ret = mipi_dsi_dcs_write(dsi, data, len);
>> +	ret = mipi_dsi_dcs_write(dsi, data[0], data + 1, len - 1);
>>  	if (ret < 0) {
>>  		dev_err(ctx->dev, "error %zd writing dcs seq: %*ph\n", ret, len,
>>  			data);
>> diff --git a/include/drm/drm_mipi_dsi.h b/include/drm/drm_mipi_dsi.h
>> index 7b5e1a9244e1..bea181121e8b 100644
>> --- a/include/drm/drm_mipi_dsi.h
>> +++ b/include/drm/drm_mipi_dsi.h
>> @@ -127,8 +127,8 @@ struct mipi_dsi_device {
>>  
>>  int mipi_dsi_attach(struct mipi_dsi_device *dsi);
>>  int mipi_dsi_detach(struct mipi_dsi_device *dsi);
>> -ssize_t mipi_dsi_dcs_write(struct mipi_dsi_device *dsi, const void *data,
>> -			    size_t len);
>> +ssize_t mipi_dsi_dcs_write(struct mipi_dsi_device *dsi, u8 cmd,
>> +			   const void *data, size_t len);
>>  ssize_t mipi_dsi_dcs_read(struct mipi_dsi_device *dsi, u8 cmd, void *data,
>>  			  size_t len);
>>  
>> -- 
>> 2.0.1
>>
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