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Message-ID: <OSBPR01MB50612C6EF774733B3496AECADFFD0@OSBPR01MB5061.jpnprd01.prod.outlook.com>
Date: Thu, 12 Mar 2020 09:44:13 +0000
From: "ashiduka@...itsu.com" <ashiduka@...itsu.com>
To: 'Geert Uytterhoeven' <geert@...ux-m68k.org>,
"gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>
CC: "erosca@...adit-jv.com" <erosca@...adit-jv.com>,
"linux-serial@...r.kernel.org" <linux-serial@...r.kernel.org>,
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<linux-renesas-soc@...r.kernel.org>,
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Subject: RE: [PATCH] serial: sh-sci: Support custom speed setting
Dear Greg, Geert,
> 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.
> > I saw the code above, I thought I wouldn't write such code normally.
> Why not?
Is it normal to declare ioctl() without "#include <sys/ioctl.h>" ?
Thanks & Best Regards,
Yuusuke Ashiduka <ashiduka@...itsu.com>
Embedded System Development Dept. Embedded System Development Div.
FUJITSU COMPUTER TECHNOLOGIES Ltd.
> -----Original Message-----
> From: Geert Uytterhoeven <geert@...ux-m68k.org>
> Sent: Thursday, March 12, 2020 6:03 PM
> To: Torii, Kenichi/鳥居 健一 <torii.ken1@...itsu.com>
> Cc: gregkh@...uxfoundation.org; erosca@...adit-jv.com;
> linux-serial@...r.kernel.org; linux-renesas-soc@...r.kernel.org;
> wsa+renesas@...g-engineering.com;
> yoshihiro.shimoda.uh@...esas.com; uli+renesas@...nd.eu;
> george_davis@...tor.com; andrew_gabbasov@...tor.com;
> jiada_wang@...tor.com; yuichi.kusakabe@...so-ten.com;
> yasano@...adit-jv.com; linux-kernel@...r.kernel.org;
> jslaby@...e.com; yohhei.fukui@...so-ten.com; Ashizuka, Yuusuke/
> 芦塚 雄介 <ashiduka@...itsu.com>; magnus.damm@...il.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@...itsu.com
> <torii.ken1@...itsu.com> wrote:
> > On Tue, 11 Feb 2020 05:57:35 +0900,
> > Greg Kroah-Hartman wrote:
> > > On Thu, Jan 30, 2020 at 01:32:50PM +0100, Geert Uytterhoeven
> wrote:
> > > > On Wed, Jan 29, 2020 at 5:20 PM Eugeniu Rosca
> <erosca@...adit-jv.com> wrote:
> > > > > From: Torii Kenichi <torii.ken1@...fujitsu.com>
> > > > >
> > > > > This patch is necessary to use BT module and XM module with
> DENSO TEN
> > > > > development board.
> > > > >
> > > > > This patch supports ASYNC_SPD_CUST flag by ioctl(TIOCSSERIAL),
> enables
> > > > > custom speed setting with setserial(1).
> > > > >
> > > > > The custom speed is calculated from uartclk and
> custom_divisor.
> > > > > If custom_divisor is zero, custom speed setting is invalid.
> > > > >
> > > > > Signed-off-by: Torii Kenichi <torii.ken1@...fujitsu.com>
> > > > > [erosca: rebase against v5.5]
> > > > > Signed-off-by: Eugeniu Rosca <erosca@...adit-jv.com>
> > > >
> > > > Thanks for your patch!
> > > >
> > > > While this seems to work fine[*], I have a few
> comments/questions:
> > > > 1. This feature seems to be deprecated:
> > > >
> > > > sh-sci e6e68000.serial: setserial sets custom speed
> on
> > > > ttySC1. This is deprecated.
> > > >
> > > > 2. As the wanted speed is specified as a divider, the resulting
> speed
> > > > may be off, cfr. the example for 57600 below.
> > > > Note that the SCIF device has multiple clock inputs, and
> can do
> > > > 57600 perfectly if the right crystal has been fitted.
> > > >
> > > > 3. What to do with "[PATCH/RFC] serial: sh-sci: Update uartclk
> based
> > > > on selected clock"
> (https://patchwork.kernel.org/patch/11103703/)?
> > > > Combined with this, things become pretty complicated and
> > > > unpredictable, as uartclk now always reflect the frequency
> of the
> > > > last used base clock, which was the optimal one for the
> previously
> > > > used speed....
> > > >
> > > > I think it would be easier if we just had an API to specify
> a raw speed.
> > > > 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.
> >
> > >#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@...ux-m68k.org
>
> In personal conversations with technical people, I call myself a
> hacker. But
> when I'm talking to journalists I just say "programmer" or something
> like that.
> -- Linus Torvalds
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