linux-kernel - Re: [PATCH 3/3] drm/panel: add panel driver for Xinpeng XPP055C272 panels

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Date:   Sun, 15 Dec 2019 00:07:49 +0100
From:   Heiko Stübner <heiko@...ech.de>
To:     Sam Ravnborg <sam@...nborg.org>
Cc:     thierry.reding@...il.com, mark.rutland@....com,
        devicetree@...r.kernel.org,
        Heiko Stuebner <heiko.stuebner@...obroma-systems.com>,
        linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        robh+dt@...nel.org, christoph.muellner@...obroma-systems.com
Subject: Re: [PATCH 3/3] drm/panel: add panel driver for Xinpeng XPP055C272 panels

Hi Sam,

thanks for the thorough review :-)

Am Samstag, 14. Dezember 2019, 09:17:30 CET schrieb Sam Ravnborg:
> > +#define dsi_generic_write_seq(dsi, cmd, seq...) do {			\
> > +		static const u8 d[] = { seq };				\
> > +		int ret;						\
> > +		ret = mipi_dsi_dcs_write(dsi, cmd, d, ARRAY_SIZE(d));	\
> > +		if (ret < 0)						\
> > +			return ret;					\
> > +	} while (0)
> This macro return an error code if a write fails.
> 
> > +
> > +static int xpp055c272_init_sequence(struct xpp055c272 *ctx)
> > +{
> > +	struct mipi_dsi_device *dsi = to_mipi_dsi_device(ctx->dev);
> > +	struct device *dev = ctx->dev;
> > +	int ret;
> > +
> > +	/*
> > +	 * Init sequence was supplied by the panel vendor without much
> > +	 * documentation.
> > +	 */
> > +	dsi_generic_write_seq(dsi, XPP055C272_CMD_SETEXTC, 0xf1, 0x12, 0x83);
> But all uses of the macro here ignore the error.

hmm, am I way off track here?

	dsi_generic_write_seq(dsi, XPP055C272_CMD_SETEXTC, 0xf1, 0x12, 0x83);
	dsi_generic_write_seq(dsi, XPP055C272_CMD_SETMIPI,
			      0x33, 0x81, 0x05, 0xf9, 0x0e, 0x0e, 0x00, 0x00,
			      0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x44, 0x25,
			      0x00, 0x91, 0x0a, 0x00, 0x00, 0x02, 0x4f, 0x01,
			      0x00, 0x00, 0x37);
	...

should just expand to

do {
		static const u8 d[] = { 0xf1, 0x12, 0x83 };
		int ret;
		ret = mipi_dsi_dcs_write(dsi, XPP055C272_CMD_SETEXTC, d, ARRAY_SIZE(d));
		if (ret < 0)
			return ret;
} while (0)
do {
		static const u8 d[] = { 0x33, 0x81, 0x05, 0xf9, 0x0e, 0x0e, 0x00, 0x00,
			      0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x44, 0x25,
			      0x00, 0x91, 0x0a, 0x00, 0x00, 0x02, 0x4f, 0x01,
			      0x00, 0x00, 0x37 };
		int ret;
		ret = mipi_dsi_dcs_write(dsi, XPP055C272_CMD_SETMIPI, d, ARRAY_SIZE(d));
		if (ret < 0)
			return ret;
} while (0)
...

so every write instance will actually return an error if it happens and not
continue on with the next init item.

Or I'm not thinking correctly at 0:07 ;-)


Heiko