Hi Hans, On Wed, Aug 03, 2022 at 11:19:31AM +0200, Hans Verkuil wrote: > On 03/08/2022 11:14, Laurent Pinchart wrote: > > Hi Erling, > > > > (CC'ing the linux-i2c mailing list and Srinivas, the maintainer of the > > nvmem framework) > > > > Thank you for the patches. > > > > On Wed, Aug 03, 2022 at 09:58:45AM +0200, Erling Ljunggren wrote: > >> This series adds support for the standalone cat24c208 EDID EEPROM i2c device. > >> Usually EDID support is part of an HDMI receiver, but this is a standalone EEPROM. > >> > >> Note that EEPROMs for EDIDs are not regular EEPROM devices, these are dual port > >> devices that follow the VESA E-DDC standard. > >> > >> Since this is a standalone device that does not capture any video a new > >> V4L2_CAP_EDID_MEMORY capability is introduced to represent such devices. > >> Note that such a device doesn't have to be an EEPROM, it can also be > >> implemented using a microcontroller, for example. Hence the use of the generic > >> word 'MEMORY'. > > > > Why can't this be exposed as a nvmem device, like other types of eeproms > > here ? > > Because it isn't. Same discussion I had with Andy: it's not a regular eeprom but > a dedicated eeprom for EDIDs. And we have support for that already in V4L2. It's > specific to receivers as well, so the only subsystem it belongs to is V4L2. Why does that matter ? It's still an NVMEM device that stores 512 bytes of data, even if the I2C interface to read/write it is different than other types of standard EEPROMs. > See the discussion I had with Andy on this: > > https://patchwork.linuxtv.org/project/linux-media/patch/20220728114050.2400475-5-hljunggr@xxxxxxxxx/ > > >> The new capability uses the free bit 0x00000008. But we are running out of > >> capability bits: only 0x40000000 and 0x00000008 are free at the moment. > >> > >> There is one other capability V4L2_CAP_ASYNCIO (0x02000000) that is not used > >> at all, it was never implemented. Wouldn't it be better to define > >> V4L2_CAP_ASYNCIO to 0, mark it as obsolete, and instead reuse it for this > >> V4L2_CAP_EDID_MEMORY capability? > >> > >> v2: > >> - fix dt binding example > >> - rename i2c client variables in data struct > >> - fix include: of_device.h -> mod_devicetable.h > >> - Sorted makefile > >> - used define EDID_OFFSET_EXT_FLAG instead of magic number > >> - removed of_match_ptr > >> - added bus_info > >> - remove unneeded headers > >> - add depends on OF to Kconfig > >> > >> Erling Ljunggren (4): > >> media: videodev2.h: add V4L2_CAP_EDID_MEMORY > >> media: docs: Add V4L2_CAP_EDID_MEMORY > >> dt-bindings: media: add cat24c208 bindings > >> media: v4l2-dev: handle V4L2_CAP_EDID_MEMORY > >> > >> Jonathan Selnes (1): > >> media: i2c: cat24c208: driver for the cat24c208 EDID EEPROM > >> > >> .../bindings/media/i2c/onnn,cat24c208.yaml | 40 ++ > >> .../userspace-api/media/v4l/biblio.rst | 11 + > >> .../media/v4l/vidioc-querycap.rst | 7 + > >> .../media/videodev2.h.rst.exceptions | 1 + > >> MAINTAINERS | 7 + > >> drivers/media/i2c/Kconfig | 9 + > >> drivers/media/i2c/Makefile | 1 + > >> drivers/media/i2c/cat24c208.c | 421 ++++++++++++++++++ > >> drivers/media/v4l2-core/v4l2-dev.c | 8 + > >> include/uapi/linux/videodev2.h | 1 + > >> 10 files changed, 506 insertions(+) > >> create mode 100644 Documentation/devicetree/bindings/media/i2c/onnn,cat24c208.yaml > >> create mode 100644 drivers/media/i2c/cat24c208.c -- Regards, Laurent Pinchart
