Hi HeungJun, On 12/29/2011 06:08 AM, HeungJun, Kim wrote: >> -----Original Message----- >> From: linux-media-owner@xxxxxxxxxxxxxxx [mailto:linux-media- >> owner@xxxxxxxxxxxxxxx] On Behalf Of Laurent Pinchart >> Sent: Wednesday, December 28, 2011 10:52 PM >> To: Sylwester Nawrocki >> Cc: HeungJun, Kim; linux-media@xxxxxxxxxxxxxxx; mchehab@xxxxxxxxxx; >> hverkuil@xxxxxxxxx; sakari.ailus@xxxxxx; kyungmin.park@xxxxxxxxxxx; Hans de >> Goede >> Subject: Re: [RFC PATCH 1/4] v4l: Add V4L2_CID_PRESET_WHITE_BALANCE menu >> control >> >> Hi, >> >> On Wednesday 28 December 2011 14:35:00 Sylwester Nawrocki wrote: >>> On 12/28/2011 07:23 AM, HeungJun, Kim wrote: >>>> It adds the new CID for setting White Balance Preset. This CID is >>>> provided as menu type using the following items: >>>> 0 - V4L2_WHITE_BALANCE_INCANDESCENT, >>>> 1 - V4L2_WHITE_BALANCE_FLUORESCENT, >>>> 2 - V4L2_WHITE_BALANCE_DAYLIGHT, >>>> 3 - V4L2_WHITE_BALANCE_CLOUDY, >>>> 4 - V4L2_WHITE_BALANCE_SHADE, >>> >>> I have been also investigating those white balance presets recently and >>> noticed they're also needed for the pwc driver. Looking at >>> drivers/media/video/pwc/pwc-v4l2.c there is something like: >>> >>> const char * const pwc_auto_whitebal_qmenu[] = { >>> "Indoor (Incandescant Lighting) Mode", >>> "Outdoor (Sunlight) Mode", >>> "Indoor (Fluorescent Lighting) Mode", >>> "Manual Mode", >>> "Auto Mode", >>> NULL >>> }; >>> >>> static const struct v4l2_ctrl_config pwc_auto_white_balance_cfg = { >>> .ops = &pwc_ctrl_ops, >>> .id = V4L2_CID_AUTO_WHITE_BALANCE, >>> .type = V4L2_CTRL_TYPE_MENU, >>> .max = awb_auto, >>> .qmenu = pwc_auto_whitebal_qmenu, >>> }; >>> >>> ... >>> >>> cfg = pwc_auto_white_balance_cfg; >>> cfg.name = v4l2_ctrl_get_name(cfg.id); >>> cfg.def = def; >>> pdev->auto_white_balance = v4l2_ctrl_new_custom(hdl, &cfg, NULL); >>> >>> So this driver re-defines V4L2_CID_AUTO_WHITE_BALANCE as a menu control >>> with custom entries. That's interesting... However it works in practice >>> and applications have access to what's provided by hardware. >>> Perhaps V4L2_CID_AUTO_WHITE_BALANCE_TEMPERATURE would be a better fit for >>> that :) >>> >>> Nevertheless, redefining standard controls in particular drivers sounds >>> a little dubious. I wonder if this is a generally agreed approach ? >> >> No agreed with me at least :-) > > I guess the WBP menu controls of pwc driver is probably defined in the other > headers, for users being well known the PWC hardware. So it should be managed > separately to videodev2.h. Is it right? Even if the way might be slightly > different, it can't avoid to be "managed separately". > > It means the users being not well known the specific hardware like PWC, > have difficulty to use that driver well. > And, at least, It doesn't looks generic API for me. > In this case, the unfamiliar user with such unique hardware, can use > whatever he wants to use finally, after finding & looking around the headers. Applications can query drivers for supported controls and populate user control panels dynamically, based on information from VIDIOC_QUERYCTRL and VIDIOC_QUERYMENU ioctls. Not needing to rely on menu items definition in videodev2.h. I had a feeling you weren't considering such case. :) Perhaps it's uncommon in embedded systems though. -- Regards, Sylwester -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
