Mon, Mar 30, 2020 at 07:43:09AM +0000, ashiduka@fujitsu.com kirjoitti:

Dear Greg, Geert,

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Right.
Adding "#include <sys/ioctl.h>" to Greg's sample code causes a
compilation error.

<snip>

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Is it normal to declare ioctl() without "#include <sys/ioctl.h>" ?

I would be happy if you could give me some comments.

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http://www.panix.com/~grante/arbitrary-baud.c

We think this sample code is no good.
Should I work on glibc changes instead of kernel fixes?

Side note: I hope introducing spd_cust hack hadn't made upstream.

To the point. Use BOTHER as in code excerpt. Yes, there is a problematic parts
with the headers regarding to this feature. But you may look how others solve
it.

https://github.com/npat-efault/picocom/blob/master/termios2.txt

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Subject: RE: [PATCH] serial: sh-sci: Support custom speed setting

Dear Greg, Geert,

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I guess you mean the forward declaration of ioctrl()?
No, they should include <sys/ioctl.h> instead.

Right.
Adding "#include <sys/ioctl.h>" to Greg's sample code causes a
compilation error.

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I saw the code above, I thought I wouldn't write such code

normally.

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Why not?

Is it normal to declare ioctl() without "#include <sys/ioctl.h>" ?

Thanks & Best Regards,
Yuusuke Ashiduka [off-list ref]
Embedded System Development Dept. Embedded System Development Div.
FUJITSU COMPUTER TECHNOLOGIES Ltd.

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-----Original Message-----
From: Geert Uytterhoeven <geert@linux-m68k.org>
Sent: Thursday, March 12, 2020 6:03 PM
To: Torii, Kenichi/鳥居 健一 <redacted>
Cc: gregkh@linuxfoundation.org; erosca@de.adit-jv.com;
linux-serial@vger.kernel.org;

linux-renesas-soc@vger.kernel.org;

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wsa+renesas@sang-engineering.com;
yoshihiro.shimoda.uh@renesas.com; uli+renesas@fpond.eu;
george_davis@mentor.com; andrew_gabbasov@mentor.com;
jiada_wang@mentor.com; yuichi.kusakabe@denso-ten.com;
yasano@jp.adit-jv.com; linux-kernel@vger.kernel.org;
jslaby@suse.com; yohhei.fukui@denso-ten.com; Ashizuka, Yuusuke/
芦塚 雄介 [off-list ref]; magnus.damm@gmail.com
Subject: Re: [PATCH] serial: sh-sci: Support custom speed setting

Hi Torii-san,

On Thu, Mar 12, 2020 at 6:10 AM torii.ken1@fujitsu.com
[off-list ref] wrote:

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On Tue, 11 Feb 2020 05:57:35 +0900,
Greg Kroah-Hartman wrote:

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On Thu, Jan 30, 2020 at 01:32:50PM +0100, Geert Uytterhoeven

wrote:

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On Wed, Jan 29, 2020 at 5:20 PM Eugeniu Rosca

[off-list ref] wrote:

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From: Torii Kenichi <redacted>

This patch is necessary to use BT module and XM module

with

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DENSO TEN

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development board.

This patch supports ASYNC_SPD_CUST flag by

ioctl(TIOCSSERIAL),

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enables

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custom speed setting with setserial(1).

The custom speed is calculated from uartclk and

custom_divisor.

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If custom_divisor is zero, custom speed setting is invalid.

Signed-off-by: Torii Kenichi <redacted>
[erosca: rebase against v5.5]
Signed-off-by: Eugeniu Rosca <redacted>

Thanks for your patch!

While this seems to work fine[*], I have a few

comments/questions:

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  1. This feature seems to be deprecated:

         sh-sci e6e68000.serial: setserial sets custom speed

on

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ttySC1. This is deprecated.

  2. As the wanted speed is specified as a divider, the

resulting

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speed

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     may be off, cfr. the example for 57600 below.
     Note that the SCIF device has multiple clock inputs,

and

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can do

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     57600 perfectly if the right crystal has been fitted.

 3. What to do with "[PATCH/RFC] serial: sh-sci: Update

uartclk

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based

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     on selected clock"

(https://patchwork.kernel.org/patch/11103703/)?

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     Combined with this, things become pretty complicated

and

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     unpredictable, as uartclk now always reflect the

frequency

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of the

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     last used base clock, which was the optimal one for the

previously

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     used speed....

I think it would be easier if we just had an API to specify

a raw speed.

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Perhaps that already exists?

Yes, see:
      http://www.panix.com/~grante/arbitrary-baud.c

I saw the code above, I thought I wouldn't write such code

normally.

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#include <linux/termios.h>

int ioctl(int d, int request, ...);

Do application programmers have to accept this bad code?

I guess you mean the forward declaration of ioctrl()?
No, they should include <sys/ioctl.h> instead.

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 --
geert@linux-m68k.org

In personal conversations with technical people, I call myself

a

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hacker. But
when I'm talking to journalists I just say "programmer" or

something

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like that.
                                -- Linus Torvalds

-- 
With Best Regards,
Andy Shevchenko