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

[Marek Vasut <marex@denx.de>]

On 02/22/2018 09:53 PM, Heinrich Schuchardt wrote:
> 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

So this is only usable if you have display connected to the board ?

>> 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.

Ha

>>> - 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.

But there is no xterm ?

>>> 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

So vt100 , OK.

>>> 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@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.

At least the part which looks like ad-hoc implementation of memcpy() ,
any other cleanups are welcome.

-- 
Best regards,
Marek Vasut