Re: 2 more fbcon rotation bugs

["Antonino A. Daplas" <adaplas@gmail.com>]

Knut Petersen wrote:
> Hi Antonino,
> 
> For rotation values of 1 and 3 in combination with unusual font heights
> there are
> serious cursor problems:
> 
>    standard 8x16 and arial 22x24: ok
>    comic 16x26 and bitstream 16x30: broken as described below.
> 
> 1: Load e.g. bitstream 16x30 font and switch to rotation 1.
> 2: At the bash prompt, type "asdf  > qwer" without the quotation marks
> and without
>    hitting enter.
> 3: Try to delete the letters q,w,e,r and reenter them. Everything works
> fine.
> 4: Now place the cursor immediately behind the letter f and delete it.
> Everything ok.
> 5. Hit the key f to reenter that letter .... now something breaks:
>    a: an f is inserted at the correct position
>    b: an f flashes for a short period at the place of the first space,
> then it is overwritten
>        by the correct space character and the blinking cursor
>    c: the > at the right of the cursor is permanently overwritten with a
> blank and a
>        frozen underline of the cursor, the line now reads asdf _ _ qwer.
> 
> Deleting and reinserting the other characters before the > gives similar
> results, e.g.
> for the letter s the result is "asdd > qwer", the first d switching from
> s to d fast but
> visible and with the blinking cursor, the 2nd d (that should be an f)
> permanently
> underlined.
> 
> No problems are visible if only one string of letters (even a long one)
> is entered and
> edited  at the bash prompt.
> 
> Any idea where to start? Can you reproduce the odd behaviour?

This one I cannot reproduce. Have you tried reproducing it with vesafb?
Any message in the log, such as a kernel oops?  Your description sounds
like a corruption of cursor->mask and cursor->image.data.

> My first
> idea was
> to look into ccw_cursor() and cw_cursor(), but as there are no errors
> for long strings
> if they do not contain spaces, > or other signs of a special meaning to
> bash, I suppose
> that this is not the right/only place to start. My system is slow (Via
> Eden cpu, 533Mhz),
> could it be that the bug is invisible on faster machines? ...

You can also try enabling a non-blinking block cursor
(Documentation/VGA-softcursor.txt) to isolate the problem. With a
non-blinking block cursor, fbcon's cursor is disabled and vt.c's softcursor
takes over.  

You also said that the cursor becomes fixed.  You can comment out the call
to ops->cursor in fb_flashcursor in fbcon.c so you get a fixed cursor and
eliminate the cursor blink pathway from the debugging.

Tony


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