Re: [PATCH v8 2/6] video: add of helper for videomode

Alexey Klimov
2012-11-12T19:00:38Z

Hello Steffen,

On Mon, Nov 12, 2012 at 7:37 PM, Steffen Trumtrar
<s.trumtrar@pengutronix.de> wrote:
> This adds support for reading display timings from DT or/and convert one of those
> timings to a videomode.
> The of_display_timing implementation supports multiple children where each
> property can have up to 3 values. All children are read into an array, that
> can be queried.
> of_get_videomode converts exactly one of that timings to a struct videomode.
>
> Signed-off-by: Steffen Trumtrar <s.trumtrar@pengutronix.de>
> Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
> ---
> .../devicetree/bindings/video/display-timings.txt | 107 +++++++++++
> drivers/video/Kconfig | 13 ++
> drivers/video/Makefile | 2 +
> drivers/video/of_display_timing.c | 186 ++++++++++++++++++++
> drivers/video/of_videomode.c | 47 +++++
> include/linux/of_display_timings.h | 19 ++
> include/linux/of_videomode.h | 15 ++
> 7 files changed, 389 insertions(+)
> create mode 100644 Documentation/devicetree/bindings/video/display-timings.txt
> create mode 100644 drivers/video/of_display_timing.c
> create mode 100644 drivers/video/of_videomode.c
> create mode 100644 include/linux/of_display_timings.h
> create mode 100644 include/linux/of_videomode.h
>
> diff --git a/Documentation/devicetree/bindings/video/display-timings.txt b/Documentation/devicetree/bindings/video/display-timings.txt
> new file mode 100644
> index 0000000..e22e2fd
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/video/display-timings.txt
> @@ -0,0 +1,107 @@
> +display-timings bindings
> +========================
> +
> +display-timings-node
> +--------------------
> +
> +required properties:
> + - none
> +
> +optional properties:
> + - native-mode: the native mode for the display, in case multiple modes are
> + provided. When omitted, assume the first node is the native.
> +
> +timings-subnode
> +---------------
> +
> +required properties:
> + - hactive, vactive: Display resolution
> + - hfront-porch, hback-porch, hsync-len: Horizontal Display timing parameters
> + in pixels
> + vfront-porch, vback-porch, vsync-len: Vertical display timing parameters in
> + lines
> + - clock-frequency: displayclock in Hz
> +
> +optional properties:
> + - hsync-active : Hsync pulse is active low/high/ignored
> + - vsync-active : Vsync pulse is active low/high/ignored
> + - de-active : Data-Enable pulse is active low/high/ignored
> + - pixelclk-inverted : pixelclock is inverted/non-inverted/ignored
> + - interlaced (bool)
> + - doublescan (bool)
> +
> +All the optional properties that are not bool follow the following logic:
> + <1> : high active
> + <0> : low active
> + omitted : not used on hardware
> +
> +There are different ways of describing the capabilities of a display. The devicetree
> +representation corresponds to the one commonly found in datasheets for displays.
> +If a display supports multiple signal timings, the native-mode can be specified.
> +
> +The parameters are defined as
> +
> +struct display_timing
> +=====================
> +
> + +----------+---------------------------------------------+----------+-------+
> + | | ↑ | | |
> + | | |vback_porch | | |
> + | | ↓ | | |
> + +----------###############################################----------+-------+
> + | # ↑ # | |
> + | # | # | |
> + | hback # | # hfront | hsync |
> + | porch # | hactive # porch | len |
> + |<-------->#<---------------+--------------------------->#<-------->|<----->|
> + | # | # | |
> + | # |vactive # | |
> + | # | # | |
> + | # ↓ # | |
> + +----------###############################################----------+-------+
> + | | ↑ | | |
> + | | |vfront_porch | | |
> + | | ↓ | | |
> + +----------+---------------------------------------------+----------+-------+
> + | | ↑ | | |
> + | | |vsync_len | | |
> + | | ↓ | | |
> + +----------+---------------------------------------------+----------+-------+
> +
> +
> +Example:
> +
> + display-timings {
> + native-mode = <&timing0>;
> + timing0: 1920p24 {
> + /* 1920x1080p24 */
> + clock-frequency = <52000000>;
> + hactive = <1920>;
> + vactive = <1080>;
> + hfront-porch = <25>;
> + hback-porch = <25>;
> + hsync-len = <25>;
> + vback-porch = <2>;
> + vfront-porch = <2>;
> + vsync-len = <2>;
> + hsync-active = <1>;
> + };
> + };
> +
> +Every required property also supports the use of ranges, so the commonly used
> +datasheet description with <min typ max>-tuples can be used.
> +
> +Example:
> +
> + timing1: timing {
> + /* 1920x1080p24 */
> + clock-frequency = <148500000>;
> + hactive = <1920>;
> + vactive = <1080>;
> + hsync-len = <0 44 60>;
> + hfront-porch = <80 88 95>;
> + hback-porch = <100 148 160>;
> + vfront-porch = <0 4 6>;
> + vback-porch = <0 36 50>;
> + vsync-len = <0 5 6>;
> + };
> diff --git a/drivers/video/Kconfig b/drivers/video/Kconfig
> index 2a23b18..a324457 100644
> --- a/drivers/video/Kconfig
> +++ b/drivers/video/Kconfig
> @@ -39,6 +39,19 @@ config DISPLAY_TIMING
> config VIDEOMODE
> bool
>
> +config OF_DISPLAY_TIMING
> + def_bool y
> + select DISPLAY_TIMING
> + help
> + helper to parse display timings from the devicetree
> +
> +config OF_VIDEOMODE
> + def_bool y
> + select VIDEOMODE
> + select OF_DISPLAY_TIMING
> + help
> + helper to get videomodes from the devicetree
> +
> menuconfig FB
> tristate "Support for frame buffer devices"
> ---help---
> diff --git a/drivers/video/Makefile b/drivers/video/Makefile
> index fc30439..b936b00 100644
> --- a/drivers/video/Makefile
> +++ b/drivers/video/Makefile
> @@ -168,4 +168,6 @@ obj-$(CONFIG_FB_VIRTUAL) += vfb.o
> #video output switch sysfs driver
> obj-$(CONFIG_VIDEO_OUTPUT_CONTROL) += output.o
> obj-$(CONFIG_DISPLAY_TIMING) += display_timing.o
> +obj-$(CONFIG_OF_DISPLAY_TIMING) += of_display_timing.o
> obj-$(CONFIG_VIDEOMODE) += videomode.o
> +obj-$(CONFIG_OF_VIDEOMODE) += of_videomode.o
> diff --git a/drivers/video/of_display_timing.c b/drivers/video/of_display_timing.c
> new file mode 100644
> index 0000000..0bd30cc
> --- /dev/null
> +++ b/drivers/video/of_display_timing.c
> @@ -0,0 +1,186 @@
> +/*
> + * OF helpers for parsing display timings
> + *
> + * Copyright (c) 2012 Steffen Trumtrar <s.trumtrar@pengutronix.de>, Pengutronix
> + *
> + * based on of_videomode.c by Sascha Hauer <s.hauer@pengutronix.de>
> + *
> + * This file is released under the GPLv2
> + */
> +#include <linux/of.h>
> +#include <linux/slab.h>
> +#include <linux/export.h>
> +#include <linux/of_display_timings.h>
> +
> +/**
> + * parse_property - parse timing_entry from device_node
> + * @np: device_node with the property
> + * @name: name of the property
> + * @result: will be set to the return value
> + *
> + * DESCRIPTION:
> + * Every display_timing can be specified with either just the typical value or
> + * a range consisting of min/typ/max. This function helps handling this
> + **/
> +static int parse_property(struct device_node *np, char *name,
> + struct timing_entry *result)
> +{
> + struct property *prop;
> + int length, cells, ret;
> +
> + prop = of_find_property(np, name, &length);
> + if (!prop) {
> + pr_err("%s: could not find property %s\n", __func__, name);
> + return -EINVAL;
> + }
> +
> + cells = length / sizeof(u32);
> + if (cells == 1) {
> + ret = of_property_read_u32(np, name, &result->typ);
> + result->min = result->typ;
> + result->max = result->typ;
> + } else if (cells == 3) {
> + ret = of_property_read_u32_array(np, name, &result->min, cells);
> + } else {
> + pr_err("%s: illegal timing specification in %s\n", __func__, name);
> + return -EINVAL;
> + }
> +
> + return ret;
> +}
> +
> +/**
> + * of_get_display_timing - parse display_timing entry from device_node
> + * @np: device_node with the properties
> + **/
> +static struct display_timing *of_get_display_timing(struct device_node *np)
> +{
> + struct display_timing *dt;
> + int ret = 0;
> +
> + dt = kzalloc(sizeof(*dt), GFP_KERNEL);
> + if (!dt) {
> + pr_err("%s: could not allocate display_timing struct\n", __func__);
> + return NULL;
> + }
> +
> + ret |= parse_property(np, "hback-porch", &dt->hback_porch);
> + ret |= parse_property(np, "hfront-porch", &dt->hfront_porch);
> + ret |= parse_property(np, "hactive", &dt->hactive);
> + ret |= parse_property(np, "hsync-len", &dt->hsync_len);
> + ret |= parse_property(np, "vback-porch", &dt->vback_porch);
> + ret |= parse_property(np, "vfront-porch", &dt->vfront_porch);
> + ret |= parse_property(np, "vactive", &dt->vactive);
> + ret |= parse_property(np, "vsync-len", &dt->vsync_len);
> + ret |= parse_property(np, "clock-frequency", &dt->pixelclock);
> +
> + of_property_read_u32(np, "vsync-active", &dt->vsync_pol_active);
> + of_property_read_u32(np, "hsync-active", &dt->hsync_pol_active);
> + of_property_read_u32(np, "de-active", &dt->de_pol_active);
> + of_property_read_u32(np, "pixelclk-inverted", &dt->pixelclk_pol);
> + dt->interlaced = of_property_read_bool(np, "interlaced");
> + dt->doublescan = of_property_read_bool(np, "doublescan");
> +
> + if (ret) {
> + pr_err("%s: error reading timing properties\n", __func__);
> + return NULL;
> + }
> +
> + return dt;
> +}
> +
> +/**
> + * of_get_display_timings - parse all display_timing entries from a device_node
> + * @np: device_node with the subnodes
> + **/
> +struct display_timings *of_get_display_timings(struct device_node *np)
> +{
> + struct device_node *timings_np;
> + struct device_node *entry;
> + struct device_node *native_mode;
> + struct display_timings *disp;
> +
> + if (!np) {
> + pr_err("%s: no devicenode given\n", __func__);
> + return NULL;
> + }
> +
> + timings_np = of_find_node_by_name(np, "display-timings");
> + if (!timings_np) {
> + pr_err("%s: could not find display-timings node\n", __func__);
> + return NULL;
> + }
> +
> + disp = kzalloc(sizeof(*disp), GFP_KERNEL);
> + if (!disp)
> + return -ENOMEM;
> +
> + entry = of_parse_phandle(timings_np, "native-mode", 0);
> + /* assume first child as native mode if none provided */
> + if (!entry)
> + entry = of_get_next_child(np, NULL);
> + if (!entry) {
> + pr_err("%s: no timing specifications given\n", __func__);
> + return NULL;
> + }
> +
> + pr_info("%s: using %s as default timing\n", __func__, entry->name);
> +
> + native_mode = entry;
> +
> + disp->num_timings = of_get_child_count(timings_np);
> + disp->timings = kzalloc(sizeof(struct display_timing *)*disp->num_timings,
> + GFP_KERNEL);
> + if (!disp->timings)
> + return -ENOMEM;

Could you please check return values here ^^^ and above "disp =
kzalloc(sizeof(*disp), GFP_KERNEL);" ?
May be it's better to return NULL instead of -ENOMEM and put error message?

--
Best regards, Klimov Alexey