Re: [PATCH v6 10/14] drm/panel: add S6E3FA0 driver

[Thierry Reding <thierry.reding@gmail.com>]

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On Fri, Jul 18, 2014 at 10:49:35AM +0900, YoungJun Cho wrote:
> Hi Thierry,
> 
> Thank you a lot for kind comments.
> 
> On 07/17/2014 07:36 PM, Thierry Reding wrote:
> > On Thu, Jul 17, 2014 at 06:01:25PM +0900, YoungJun Cho wrote:
[...]
> > >diff --git a/drivers/gpu/drm/panel/panel-s6e3fa0.c b/drivers/gpu/drm/panel/panel-s6e3fa0.c
[...]
> > >+static void s6e3fa0_set_maximum_return_packet_size(struct s6e3fa0 *ctx,
> > >+							unsigned int size)
> > >+{
> > >+	struct mipi_dsi_device *dsi = to_mipi_dsi_device(ctx->dev);
> > >+	const struct mipi_dsi_host_ops *ops = dsi->host->ops;
> > >+
> > >+	if (ops && ops->transfer) {
> > >+		unsigned char buf[] = {size, 0};
> > >+		struct mipi_dsi_msg msg = {
> > >+			.channel = dsi->channel,
> > >+			.type = MIPI_DSI_SET_MAXIMUM_RETURN_PACKET_SIZE,
> > >+			.tx_len = sizeof(buf),
> > >+			.tx_buf = buf
> > >+		};
> > >+
> > >+		ops->transfer(dsi->host, &msg);
> > >+	}
> > >+}
> >
> > The Set Maximum Return Packet Size command is a standard command, so
> > please turn that into a generic function exposed by the DSI core.
> >
> 
> For this and below standard DCS commands, you want to use generic functions,
> but I have no idea for that.
> Could you explain more detail?

The goal should be to make these standard DCS commands available to all
DSI peripherals, so the implementation should look something like this:

static int mipi_dsi_set_maximum_return_packet_size(struct mipi_dsi_device *dsi,
						   u16 size)
{
	struct mipi_dsi_msg msg;

	if (!dsi->ops || !dsi->ops->transfer)
		return -ENOSYS;

	memset(&msg, 0, sizeof(msg));
	msg.channel = dsi->channel;
	msg.type = MIPI_DSI_SET_MAXIMUM_RETURN_PACKET_SIZE;
	msg.tx_len = sizeof(size);
	msg.tx_buf = &size;

	return dsi->ops->transfer(dsi->host, &msg);
}

The above is somewhat special, since it isn't DCS. For DCS I'd suggest a
common prefix, like so:

enum mipi_dcs_tear_mode {
	MIPI_DCS_TEAR_VBLANK,
	MIPI_DCS_TEAR_BLANK,
};

static int mipi_dcs_set_tear_on(struct mipi_dsi_device *dsi,
				enum mipi_dcs_tear_mode mode)
{
	u8 data[2] = { MIPI_DSI_DCS_SET_TEAR_ON, mode };
	struct mipi_dsi_msg msg;

	if (!dsi->ops || !dsi->ops->transfer)
		return -ENOSYS;

	memset(&msg, 0, sizeof(msg));
	msg.channel = dsi->channel;
	msg.type = MIPI_DSI_DCS_SHORT_WRITE_PARAM;
	msg.tx_len = sizeof(data);
	msg.tx_buf = data;

	return dsi->ops->transfer(dsi->host, &msg);
}

Thierry

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