On 10/13/2014 12:16 PM, Thierry Reding wrote:
> From: YoungJun Cho <yj44.cho at samsung.com>
>
> This function can be used to set the maximum return packet size for a
> MIPI DSI peripheral.
>
> Signed-off-by: YoungJun Cho <yj44.cho at samsung.com>
> [treding: endianess, kerneldoc, return value]
> Signed-off-by: Thierry Reding <treding at nvidia.com>
> ---
> drivers/gpu/drm/drm_mipi_dsi.c | 30 ++++++++++++++++++++++++++++++
> include/drm/drm_mipi_dsi.h | 2 ++
> 2 files changed, 32 insertions(+)
>
> diff --git a/drivers/gpu/drm/drm_mipi_dsi.c b/drivers/gpu/drm/drm_mipi_dsi.c
> index 1702ffd07986..27fc6dac5e4a 100644
> --- a/drivers/gpu/drm/drm_mipi_dsi.c
> +++ b/drivers/gpu/drm/drm_mipi_dsi.c
> @@ -198,6 +198,36 @@ int mipi_dsi_detach(struct mipi_dsi_device *dsi)
> }
> EXPORT_SYMBOL(mipi_dsi_detach);
>
> +/*
> + * mipi_dsi_set_maximum_return_packet_size() - specify the maximum size of
> the
> + * the payload in a long packet transmitted from the peripheral back to
> the
> + * host processor
> + * @dsi: DSI peripheral device
> + * @value: the maximum size of the payload
> + *
> + * Return: 0 on success or a negative error code on failure.
> + */
> +int mipi_dsi_set_maximum_return_packet_size(struct mipi_dsi_device *dsi,
> + u16 value)
> +{
> + u8 tx[2] = { value & 0xff, value >> 8 };
> + struct mipi_dsi_msg msg;
> + ssize_t err;
> +
> + memset(&msg, 0, sizeof(msg));
> + msg.channel = dsi->channel;
> + msg.type = MIPI_DSI_SET_MAXIMUM_RETURN_PACKET_SIZE;
> + msg.tx_len = sizeof(tx);
> + msg.tx_buf = tx;
An alternative (without tx variable) could be:
__cpu_to_le16s(&value);
msg.tx_len = sizeof(value);
msg.tx_buf = &value;
But it is just pico-optimization.
> +
> + err = dsi->host->ops->transfer(dsi->host, &msg);
I guess the sequence:
if (dsi->mode_flags & MIPI_DSI_MODE_LPM)
msg.flags = MIPI_DSI_MSG_USE_LPM;
should be before this callback.
The same should be in all other helpers calling ops->transfer,
so I guess it may be good to move it all to separate function, for
example sth like:
... dsi_transfer(dsi, msg)
{
if (!ops || !ops->transfer)
return -NOSYS;
if (dsi->mode_flags & MIPI_DSI_MODE_LPM)
msg.flags = MIPI_DSI_MSG_USE_LPM;
return ops->transfer(dsi->host, msg);
}
Regards
Andrzej
> + if (err < 0)
> + return err;
> +
> + return 0;
> +}
> +EXPORT_SYMBOL(mipi_dsi_set_maximum_return_packet_size);
> +
> /**
> * mipi_dsi_dcs_write_buffer() - transmit a DCS command with payload
> * @dsi: DSI peripheral device
> diff --git a/include/drm/drm_mipi_dsi.h b/include/drm/drm_mipi_dsi.h
> index 836cc2b677d0..ef50b5d0de57 100644
> --- a/include/drm/drm_mipi_dsi.h
> +++ b/include/drm/drm_mipi_dsi.h
> @@ -132,6 +132,8 @@ static inline struct mipi_dsi_device
> *to_mipi_dsi_device(struct device *dev)
>
> int mipi_dsi_attach(struct mipi_dsi_device *dsi);
> int mipi_dsi_detach(struct mipi_dsi_device *dsi);
> +int mipi_dsi_set_maximum_return_packet_size(struct mipi_dsi_device *dsi,
> + u16 value);
> ssize_t mipi_dsi_dcs_write_buffer(struct mipi_dsi_device *dsi,
> const void *data, size_t len);
> ssize_t mipi_dsi_dcs_write(struct mipi_dsi_device *dsi, u8 cmd,
>
