[U-Boot] [PATCH 1/2] usb: kbd: allow multibyte sequences to be put into ring buffer

[Heinrich Schuchardt]

On 02/22/2018 08:55 PM, Marek Vasut wrote:
> On 02/22/2018 07:06 PM, Heinrich Schuchardt wrote:
>> On 02/22/2018 03:20 PM, Marek Vasut wrote:
>>> On 02/22/2018 01:04 PM, Heinrich Schuchardt wrote:
>>>> The USB keyboard driver provides a ring buffer for key strokes.
>>>>
>>>> Function keys cannot be encoded as single bytes. Instead xterm control
>>>> sequences have to be put into the ring buffer.
>>>
>>> Does it work without xterm or with any other terminal ?
>> I use two testing environments:
>>
>> - USB keyboard and HDMI monitor. This does not involve xterm.
> 
> So how are the "xterm control sequences" interpreted then?

I already pointed you to U-Boot function cread_line().
Here only the sequences for left, right, up, and down are used.

When starting an EFI application the xterm escape sequences are
translated to EFI scan codes. See lib/efi_loader/efi_console.c

> What happens if you use the U-Boot menu, does this work in there too?

Function bootmenu_loop() only looks for
ESC [ A and
ESC [ B

So without the patch series you are not able to navigate inside the 
U-Boot menu using a USB keyboard.

> 
>> - Connection from Linux via serial cable. Linux screen or minicom
>>    transfer xterm escape sequences when typing special keys.
> 
> Did you try this ie. on kms console , outside of X11 ?

I never heard of a kms console.

If I boot into the plain Linux console (i.e. without X11), key 
pressesare still provided as xterm escape sequences.

> 
>> My target is calling iPXE and Grub as EFI applications. For navigation
>> in Grub we need at least up, down, left, right, delete and F10. In
>> lib/efi_loader/efi_console.c xterm escape sequences are translated to
>> EFI scan codes.
> 
>> Before the patch series the U-Boot USB keyboard driver signals up, down,
>> left and right as non-standard character codes 0x6, 0x2, 0xe, 0x10.
>> F1-F12, Insert, Delete, Home, End, Page Up, and Page Down are not
>> supported.
>>
>> Function cread_line() (in common/cli_readline.c) interprets both xterm
>> escape sequences and non-standard control characters provided by the USB
>> keyboard driver.
> 
> Wait, are those xterm or vt100 sequences ?

VT100 largely overlaps with xterm. See
https://invisible-island.net/xterm/ctlseqs/ctlseqs.pdf

> 
>> JinHua Luo's patch
>> Add readline cmdline-editing extension
>> 501090aaa67b6072ebe8b721c8328d32be607660
>> which introduced command line editing unfortunately does not describe
>> why it chose CTRL+B, CTRL+F, CTRL+N, and CTRL+P for navigation. These
>> codes are not documented in any README.
>>
>>>
>>>> This preparatory patch changes function usb_kbd_put_queue() to allow
>>>> adding
>>>> multiple characters at once. If the buffer cannot accommodate the whole
>>>> sequence, it is rejected completely.
>>>>
>>>> Signed-off-by: Heinrich Schuchardt <xypron.glpk at gmx.de>
>>>> ---
>>>>    common/usb_kbd.c | 42 +++++++++++++++++++++++++-----------------
>>>>    1 file changed, 25 insertions(+), 17 deletions(-)
>>>>
>>>> diff --git a/common/usb_kbd.c b/common/usb_kbd.c
>>>> index 8cbdba6ac2..706cc350a6 100644
>>>> --- a/common/usb_kbd.c
>>>> +++ b/common/usb_kbd.c
>>>> @@ -125,24 +125,32 @@ extern int __maybe_unused net_busy_flag;
>>>>    /* The period of time between two calls of usb_kbd_testc(). */
>>>>    static unsigned long __maybe_unused kbd_testc_tms;
>>>>    -/* Puts character in the queue and sets up the in and out pointer. */
>>>> -static void usb_kbd_put_queue(struct usb_kbd_pdata *data, char c)
>>>> +/*
>>>> + * Put characters into ring buffer.
>>>> + *
>>>> + * @data:    private data
>>>> + * @buf        buffer with data to be queued
>>>> + * @count:    number of characters to be queued
>>>> + */
>>>> +static void usb_kbd_put_queue(struct usb_kbd_pdata *data,
>>>> +                  uint8_t *buf, int count)
>>>>    {
>>>> -    if (data->usb_in_pointer == USB_KBD_BUFFER_LEN - 1) {
>>>> -        /* Check for buffer full. */
>>>> -        if (data->usb_out_pointer == 0)
>>>> -            return;
>>>> -
>>>> -        data->usb_in_pointer = 0;
>>>> -    } else {
>>>> -        /* Check for buffer full. */
>>>> -        if (data->usb_in_pointer == data->usb_out_pointer - 1)
>>>> -            return;
>>>> -
>>>> -        data->usb_in_pointer++;
>>>> +    int i, used;
>>>> +
>>>> +    /* Check if buffer holds at least 'count' free slots */
>>>> +    used = data->usb_in_pointer - data->usb_out_pointer;
>>>> +    if (used < 0)
>>>> +        used += USB_KBD_BUFFER_LEN;
>>>> +    if (used + count >= USB_KBD_BUFFER_LEN)
>>>> +        return;
>>>> +
>>>> +    /* Copy to buffer */
>>>> +    for (i = 0; i < count; ++i) {
>>>> +        ++data->usb_in_pointer;
>>>> +        if (data->usb_in_pointer == USB_KBD_BUFFER_LEN)
>>>> +            data->usb_in_pointer = 0;
>>>> +        data->usb_kbd_buffer[data->usb_in_pointer] = buf[i];
>>>
>>> memcpy() ?
>>
>> Typically we copy only one byte. But escape sequences have a maximum
>> length of 8 bytes (e.g. CTRL+F8).
>>
>> We have to consider the case with wrap around. This would require two
>> memcpy() calls.
>>
>> The coding would neither get faster in the average nor less complex
>> using memcpy(). So let's keep it as it is.
> 
> I suspect this block of code needs cleanup .
> 

Could you, please, give some indication of what you dislike.

Regards

Heinrich