Re: no ioctls for serial ports? [was Re: LANANA: To Pending DeviceNum

Abramo Bagnara
2001-05-20T15:01:22Z

Alexander Viro wrote:
>
> On Sun, 20 May 2001, Abramo Bagnara wrote:
>
> > > It may have several. Which one?
> >
> > Can you explain better this?
>
> Example: console. You want to be able to pass font changes. I'm
> less than sure that putting them on the same channel as, e.g.,
> keyboard mapping changes is a good idea. We can do it, but I don't
> see why it's natural thing to do. Moreover, you already have
> /dev/vcs<n> and /dev/vcsa<n>. Can you explain what's the difference
> between them (per-VC channels) and keyboard mapping (also per-VC)?
>
> Face it, we _already_ have more than one side band.

This does not imply it's necessarily a good idea.
We are comparing

echo "9600" > /proc/self/fd/0/speed (or /dev/ttyS0/speed)
echo "8" > /proc/self/fd/0/bits (or /dev/ttyS0/bits)

with

echo -e "speed 9600\nbits 8" > /proc/self/fd/0/ioctl (or
/dev/ttyS0/ioctl).

My personal preference goes to the latter, but it's a matter of taste
(and convention choice)

(echo -n "keymap " ; cat keymap) > /dev/tty1/ioctl
(echo -n "font " ; cat font) > /dev/tty1/ioctl

This seems ugly to you?

> Moreover, we have channels that are not tied to a particular device -
> they are for a group of them. Example: setting timings for IDE controller.
> Sure, we can just say "open /dev/hda instead of /dev/hda5", but then we
> are back to the "find related file" problem you tried to avoid.

It does not seems appropriate to permit to change IDE timings using an
handle to a partition... nor it seems very safe under a permissions
point of view.

--
Abramo Bagnara mailto:abramo@alsa-project.org

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It sounds good!