From: "Ilpo Järvinen" <ilpo.jarvinen@linux.intel.com>
To: Lukas Wunner <lukas@wunner.de>
Cc: linux-serial <linux-serial@vger.kernel.org>,
Jiri Slaby <jirislaby@kernel.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
LKML <linux-kernel@vger.kernel.org>,
Johan Hovold <johan@kernel.org>,
Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
Heikki Krogerus <heikki.krogerus@linux.intel.com>,
linux-api@vger.kernel.org, Richard Henderson <rth@twiddle.net>,
Ivan Kokshaysky <ink@jurassic.park.msu.ru>,
Matt Turner <mattst88@gmail.com>,
linux-alpha@vger.kernel.org,
Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
linux-mips@vger.kernel.org,
"James E.J. Bottomley" <James.Bottomley@HansenPartnership.com>,
Helge Deller <deller@gmx.de>,
linux-parisc@vger.kernel.org,
Michael Ellerman <mpe@ellerman.id.au>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Paul Mackerras <paulus@samba.org>,
linuxppc-dev@lists.ozlabs.org,
Yoshinori Sato <ysato@users.sourceforge.jp>,
Rich Felker <dalias@libc.org>,
linux-sh@vger.kernel.org, "David S. Miller" <davem@davemloft.net>,
sparclinux@vger.kernel.org, Chris Zankel <chris@zankel.net>,
Max Filippov <jcmvbkbc@gmail.com>,
linux-xtensa@linux-xtensa.org, Arnd Bergmann <arnd@arndb.de>,
linux-arch@vger.kernel.org, linux-doc@vger.kernel.org
Subject: Re: [RFC PATCH 6/7] serial: General support for multipoint addresses
Date: Thu, 10 Mar 2022 14:29:21 +0200 (EET) [thread overview]
Message-ID: <6feb796a-ea58-9a6-f2f9-a11ca72acfd@linux.intel.com> (raw)
In-Reply-To: <20220309190521.GA9832@wunner.de>
[-- Attachment #1: Type: text/plain, Size: 1718 bytes --]
On Wed, 9 Mar 2022, Lukas Wunner wrote:
> On Mon, Mar 07, 2022 at 11:48:01AM +0200, Ilpo Järvinen wrote:
> > On Sun, 6 Mar 2022, Lukas Wunner wrote:
> > > On Wed, Mar 02, 2022 at 11:56:05AM +0200, Ilpo Järvinen wrote:
> > > > This change is necessary for supporting devices with RS485
> > > > multipoint addressing [*].
> > >
> > > If this is only used with RS485, why can't we just store the
> > > addresses in struct serial_rs485 and use the existing TIOCSRS485
> > > and TIOCGRS485 ioctls? There's 20 bytes of padding left in
> > > struct serial_rs485 which you could use. No need to add more
> > > user-space ABI.
> >
> > It could if it is agreed that serial multipoint addressing is just
> > a thing in RS-485 and nowhere else? In that case, there is no point
> > in adding more generic support for it.
>
> It's just that the above-quoted sentence in the commit message
> specifically mentions RS485.
That sentence is just to justify why addressing mode is needed,
not to take a stance on whether it is only used with RS485 or not.
> If you intend to use it with RS232
> as well, that should be made explicit, otherwise one wonders why
> it wasn't integrated into struct serial_rs485.
>
> I have no idea how common 9th bit addressing mode is with RS232.
> Goggle turns up links saying it's mainly used with RS485, "but also
> RS232". Since RS232 isn't a bus but a point-to-point link,
> 9th bit addressing doesn't seem to make as much sense.
While I don't know any better, I can image though that with an
RS232-to-RS485 converter, it could make some sense.
If I put them back to serial_rs485 / rs485 config, it's basically just
where I initially started from with this patchset (offlist).
--
i.
next prev parent reply other threads:[~2022-03-10 12:29 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-03-02 9:55 [PATCH 0/7] Add RS485 support to DW UART Ilpo Järvinen
2022-03-02 9:56 ` [PATCH 1/7] serial: 8250_dwlib: RS485 HW half duplex support Ilpo Järvinen
2022-03-06 18:48 ` Lukas Wunner
2022-03-06 22:07 ` Andy Shevchenko
2022-03-07 9:19 ` Ilpo Järvinen
2022-03-07 19:18 ` Lukas Wunner
2022-03-07 19:39 ` Andy Shevchenko
2022-03-08 12:16 ` Ilpo Järvinen
2022-03-08 12:22 ` Lukas Wunner
2022-03-08 12:59 ` Ilpo Järvinen
2022-03-08 14:50 ` Lukas Wunner
2022-03-08 14:53 ` Andy Shevchenko
2022-03-08 20:30 ` Lukas Wunner
2022-03-09 9:51 ` Ilpo Järvinen
2022-03-07 10:54 ` Ilpo Järvinen
2022-03-09 8:52 ` Lukas Wunner
2022-03-09 12:19 ` Ilpo Järvinen
2022-03-09 12:59 ` Lukas Wunner
2022-03-02 9:56 ` [PATCH 2/7] serial: 8250_dwlib: RS485 HW full " Ilpo Järvinen
2022-03-06 18:51 ` Lukas Wunner
2022-03-07 9:22 ` Ilpo Järvinen
2022-03-02 9:56 ` [RFC PATCH 3/7] serial: 8250_dwlib: Implement SW half " Ilpo Järvinen
2022-03-06 19:21 ` Lukas Wunner
2022-03-06 22:13 ` Andy Shevchenko
2022-03-02 9:56 ` [PATCH 4/7] dt_bindings: snps-dw-apb-uart: Add RS485 Ilpo Järvinen
2022-03-02 17:47 ` Rob Herring
2022-03-02 9:56 ` [RFC PATCH 5/7] serial: termbits: ADDRB to indicate 9th bit addressing mode Ilpo Järvinen
2022-03-02 9:56 ` [RFC PATCH 6/7] serial: General support for multipoint addresses Ilpo Järvinen
2022-03-06 19:40 ` Lukas Wunner
2022-03-07 9:48 ` Ilpo Järvinen
2022-03-09 19:05 ` Lukas Wunner
2022-03-10 12:29 ` Ilpo Järvinen [this message]
2022-03-10 14:09 ` Andy Shevchenko
2022-03-02 9:56 ` [RFC PATCH 7/7] serial: 8250_dwlib: Support for 9th bit multipoint addressing Ilpo Järvinen
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