Implement per-key keyboard backlight as auxdisplay?

[Werner Sembach]

Hi,

Am 19.01.24 um 11:51 schrieb Jani Nikula:
> On Fri, 19 Jan 2024, Hans de Goede <hdegoede at redhat.com> wrote:
>> For per key controllable rgb LEDs we need to discuss a coordinate
>> system. I propose using a fixed size of 16 rows of 64 keys,
>> so 64x16 in standard WxH notation.
>>
>> And then storing RGB in separate bytes, so userspace will then
>> always send a buffer of 192 bytes per line (64x3) x 14 rows
>> = 3072 bytes. With the kernel driver ignoring parts of
>> the buffer where there are no actual keys.
>>
>> I would then like the map the standard 105 key layout onto this,
>> starting at x.y (column.row) coordinates of 16.6 (with 0.0 being
>> the top left). Leaving plenty of space on the left top and right
>> (and some on the bottom) for extra media key rows, macro keys, etc.
>>
>> The idea to have the standard layout at a fixed place is to allow
>> userspace to have a database of preset patterns which will work
>> everywhere.
>>
>> Note I say standard 105 key layout, but in reality for
>> defining the standardized part of the buffer we should
>> use the maximum amount of keys per row of all the standard layouts,
>> so for row 6 (the ESC row) and for extra keys on the right outside
>> the main block we use the standard layout as shown here:
> Doesn't the input stack already have to have pretty much all of this
> already covered? I can view the keyboard layout in my desktop
> environment, and it's a reasonably accurate match, even if unlikely to
> be pixel perfect. But crucially, it has to have all the possible layouts
> covered already.
>
> And while I would personally hate it, you can imagine a use case where
> you'd like a keypress to have a visual effect around the key you
> pressed. A kind of force feedback, if you will. I don't actually know,
> and correct me if I'm wrong, but feels like implementing that outside of
> the input subsystem would be non-trivial.
>
> Cc: Dmitry, could we at least have some input from the input subsystem
> POV on this? AFAICT we have received none.
>
>
> BR,
> Jani.

Don't forget: while we are currently discussing keyboards, in the future this 
API imho should also be usefull for other RGB devices like mice, lightbars, etc.

Regards,

Werner

>
>
>> http://www.maxkeyboard.com/images/105_ISO_6_25_Key_Layout.jpg
>>
>> For the main area of the keyboard looking at:
>>
>> http://bopqehorizon.weebly.com/uploads/1/3/4/3/134337299/913246919_orig.png
>>
>> We want to max rows per key, so this means that per row we use
>> (from the above image) :
>>
>> row  7: 106/109 - JIS
>> row  8: 101/104 - ANSI
>> row  9: 102/105 - ISO
>> row 10: 104/107 - ABNT
>> row 11: 106/109 - JIS
>>
>> (with row 7 being the main area top row)
>>
>> This way we can address all the possible keys in the various
>> standard layouts in one standard wat and then the drivers can
>> just skip keys which are not there when preparing the buffer
>> to send to the hw / fw.
>>
>> One open question is if we should add padding after the main
>> area so that the printscreen / ins / del / leftarrow of the
>> "middle" block of
>>
>> http://www.maxkeyboard.com/images/105_ISO_6_25_Key_Layout.jpg
>>
>> all start at the same x (say 32) or we just pack these directly
>> after the main area.
>>
>> And the same question for the numlock block, do we align
>> this to an x of say 36, or pack it ?
>>
>>
>> As for the actual IOCTL API I think there should be
>> the following ioctls:
>>
>> 1. A get-info ioctl returning a struct with the following members:
>>
>> {
>> char name[64]      /* Keyboard model name / identifier */
>> int row_begin[16]; /* The x address of the first available key per row. On a std 105key kbd this will be 16 for rows 6-11, 0 for other rows */
>> int row_end[16];   /* x+1 for the address of the last available key per row, end - begin gives number of keys in a row */
>> int rgb_zones;     /* number of rgb zones for zoned keyboards. Note both
>>                        zones and per key addressing may be available if
>>                        effects are applied per zone. */
>> ?
>> }
>>
>> 2. A set-leds ioctl which takes the earlier discussed 3092 bytes buffer
>> to set all the LEDs at once, only valid if at least one row has a non 0 lenght.
>>
>> 3. A set-zones ioctl which takes an array of bytes sized 3 * number-of-zones
>> containing RGB values for each zone
>>
>> 4. A enum_effects ioctl which takes a struct with the following members:
>>
>> {
>> long size; /* Size of passed in struct including the size member itself */
>> long effects_mask[]
>> }
>>
>> the idea being that there is an enum with effects, which gets extended
>> as we encounter more effects and the bitmask in effects_mask has a bit set
>> for each effects enum value which is supported. effects_mask is an array
>> so that we don't run out of bits. If older userspace only passes 1 long
>> (size == (2*sizeof(long)) when 2 are needed at some point in the future
>> then the kernel will simply only fill the first long.
>>
>> 5. A set_effect ioctl which takes a struct with the following members:
>>
>> {
>> long size; /* Size of passed in struct including the size member itself */
>> int effect_nr; /* enum value of the effect to enable, 0 for disable effect */
>> int zone;  /* zone to apply the effect to */
>> int speed; /* cycle speed of the effect in milli-hz */
>> char color1[3]; /* effect dependend may be unused. */
>> char color2[3]; /* effect dependend may be unused. */
>> }
>>
>> Again the idea with the size member is that the struct can be extended with
>> new members if necessary and the kernel will supply a default value for
>> older userspaces which provide a smaller struct (note size being smaller
>> then sizeof(struct-v1) will invalid).
>>
>>
>> Note this is all just a rough sketch suggestions welcome!
>>
>> Regards,
>>
>> Hans
>>
>>
>>