On Fri, 7 Nov 2014 13:43:59 +0200
Sakari Ailus [off-list ref] wrote:

Hi Boris,

Thank you for the update.

On Thu, Nov 06, 2014 at 10:56:59AM +0100, Boris Brezillon wrote:

quoted

Rename mediabus formats and move the enum into a separate header file so
that it can be used by DRM/KMS subsystem without any reference to the V4L2
subsystem.

Old v4l2_mbus_pixelcode now points to media_bus_format.

Signed-off-by: Boris Brezillon <redacted>
Acked-by: Guennadi Liakhovetski <redacted>
---
 include/uapi/linux/Kbuild             |   1 +
 include/uapi/linux/media-bus-format.h | 131 ++++++++++++++++++++++++++++++++++
 include/uapi/linux/v4l2-mediabus.h    | 114 +----------------------------
 3 files changed, 134 insertions(+), 112 deletions(-)
 create mode 100644 include/uapi/linux/media-bus-format.h

diff --git a/include/uapi/linux/Kbuild b/include/uapi/linux/Kbuild
index b70237e..b2c23f8 100644
--- a/include/uapi/linux/Kbuild
+++ b/include/uapi/linux/Kbuild

@@ -414,6 +414,7 @@ header-y += veth.h
 header-y += vfio.h
 header-y += vhost.h
 header-y += videodev2.h
+header-y += media-bus-format.h

Could you arrange this to the list alphabetically, please?

quoted

 header-y += virtio_9p.h
 header-y += virtio_balloon.h
 header-y += virtio_blk.h

diff --git a/include/uapi/linux/media-bus-format.h b/include/uapi/linux/media-bus-format.h
new file mode 100644
index 0000000..251a902
--- /dev/null
+++ b/include/uapi/linux/media-bus-format.h

@@ -0,0 +1,131 @@
+/*
+ * Media Bus API header
+ *
+ * Copyright (C) 2009, Guennadi Liakhovetski <g.liakhovetski@gmx.de>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#ifndef __LINUX_MEDIA_BUS_FORMAT_H
+#define __LINUX_MEDIA_BUS_FORMAT_H
+
+/*
+ * These bus formats uniquely identify data formats on the data bus. Format 0
+ * is reserved, MEDIA_BUS_FMT_FIXED shall be used by host-client pairs, where
+ * the data format is fixed. Additionally, "2X8" means that one pixel is
+ * transferred in two 8-bit samples, "BE" or "LE" specify in which order those
+ * samples are transferred over the bus: "LE" means that the least significant
+ * bits are transferred first, "BE" means that the most significant bits are
+ * transferred first, and "PADHI" and "PADLO" define which bits - low or high,
+ * in the incomplete high byte, are filled with padding bits.
+ *
+ * The bus formats are grouped by type, bus_width, bits per component, samples
+ * per pixel and order of subsamples. Numerical values are sorted using generic
+ * numerical sort order (8 thus comes before 10).
+ *
+ * As their value can't change when a new bus format is inserted in the
+ * enumeration, the bus formats are explicitly given a numerical value. The next
+ * free values for each category are listed below, update them when inserting
+ * new pixel codes.
+ */
+
+#define MEDIA_BUS_FMT_ENTRY(name, val)	\
+	MEDIA_BUS_FMT_ ## name = val,	\
+	V4L2_MBUS_FMT_ ## name = val
+
+enum media_bus_format {

There's no really a need to keep the definitions inside the enum. It looks a
little bit confusing to me. That made me realise something I missed
yesterday.

There's a difference: the enum in C++ is a different thing than in C, and
the enum type isn't able to contain any other values than those defined in
the enumeration.

So what I propose is the following. Keep enum v4l2_mbus_pixelcode around,
including the enum values. Define new values for MEDIA_BUS_* equivalents
using preprocessor macros, as you've done below. Drop the definition of enum
media_bus_format, and use u32 (or uint32_t) type for the variables.

This way the enum stays intact for existing C++ applications, and new
applications will have to use a 32-bit type.

Fair enough. If Hans agree I'll rework the series and drop the
media_bus_format enum.

Thanks,

Boris

-- 
Boris Brezillon, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com