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Re: [Qemu-devel] [PATCH v4 4/4] hw/input/adb.c: implement QKeyCode suppo


From: Programmingkid
Subject: Re: [Qemu-devel] [PATCH v4 4/4] hw/input/adb.c: implement QKeyCode support
Date: Sat, 12 Mar 2016 00:40:37 -0500

On Mar 11, 2016, at 10:30 PM, Peter Maydell wrote:

> 
>> +    }
>> +    keycode = s->data[s->rptr];
>> +    if (++s->rptr == sizeof(s->data)) {
>> +        s->rptr = 0;
>>     }
>> +    s->count--;
>> +
>> +    obuf[0] = keycode;
> 
> You are still trying to put a two byte keycode (ADB_KEY_POWER)
> into this one-byte array slot. I don't know what the right way to
> send a two-byte keycode is but this is obviously not it, as
> I said before.
> 
>> +    /* NOTE: could put a second keycode if needed */
>> +    obuf[1] = 0xff;
>> +    olen = 2;
>> +
>>     return olen;
>> }

Is this ok?

    /* The power key is the only two byte value key, so it is a special case. */
    if (keycode == (ADB_KEY_POWER & 0x00ff)) {
        obuf[0] = ADB_KEY_POWER & 0x00ff;
        obuf[1] = ADB_KEY_POWER & 0xff00 >> 8;
        olen = 2;
    } else {
        obuf[0] = keycode;
        /* NOTE: could put a second keycode if needed */
        obuf[1] = 0xff;
        olen = 2;
    }

The keycode value comes from an 8 bit array so holding the full value of the 
power key is not possible. That is the reason for the "if (keycode == 
(ADB_KEY_POWER & 0x00ff))". 

The code might be a little more efficient if we did this:

    /* The power key is the only two byte value key, so it is a special case. */
    if (keycode == 0x7f) {
        obuf[0] = 0x7f;
        obuf[1] = 0x7f;
        olen = 2;
    } else {
        obuf[0] = keycode;
        /* NOTE: could put a second keycode if needed */
        obuf[1] = 0xff;
        olen = 2;
    }

The speed difference isn't noticeable so either way works well.


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