From: Lukas Wunner <lukas@wunner.de>
To: "Ilpo Järvinen" <ilpo.jarvinen@linux.intel.com>
Cc: linux-serial@vger.kernel.org, Jiri Slaby <jirislaby@kernel.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
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: Sun, 6 Mar 2022 20:40:01 +0100 [thread overview]
Message-ID: <20220306194001.GD19394@wunner.de> (raw)
In-Reply-To: <20220302095606.14818-7-ilpo.jarvinen@linux.intel.com>
On Wed, Mar 02, 2022 at 11:56:05AM +0200, Ilpo Järvinen wrote:
> This patch adds generic support for serial multipoint
> addressing. Two new ioctls are added. TIOCSADDR is used to
Nit: "This patch adds..." is superfluous. Just write "Add ..."
in imperative mood.
> 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.
> [*] Technically, RS485 is just an electronic spec and does not
> itself specify the 9th bit addressing mode but 9th bit seems
> at least "semi-standard" way to do addressing with RS485.
Is 9th bit addressing actually used by an Intel customer or was
it implemented just for feature completeness? I think this mode
isn't used often (I've never seen a use case myself), primarily
because it requires disabling parity.
Thanks,
Lukas
WARNING: multiple messages have this Message-ID (diff)
From: Lukas Wunner <lukas@wunner.de>
To: "Ilpo Järvinen" <ilpo.jarvinen@linux.intel.com>
Cc: Heikki Krogerus <heikki.krogerus@linux.intel.com>,
linux-sh@vger.kernel.org, linux-kernel@vger.kernel.org,
"James E.J. Bottomley" <James.Bottomley@HansenPartnership.com>,
Max Filippov <jcmvbkbc@gmail.com>, Rich Felker <dalias@libc.org>,
Paul Mackerras <paulus@samba.org>,
sparclinux@vger.kernel.org, linux-api@vger.kernel.org,
Jiri Slaby <jirislaby@kernel.org>,
linux-arch@vger.kernel.org,
Yoshinori Sato <ysato@users.sourceforge.jp>,
Helge Deller <deller@gmx.de>,
linux-doc@vger.kernel.org, linux-serial@vger.kernel.org,
Matt Turner <mattst88@gmail.com>,
linux-xtensa@linux-xtensa.org, Arnd Bergmann <arnd@arndb.de>,
Johan Hovold <johan@kernel.org>,
Ivan Kokshaysky <ink@jurassic.park.msu.ru>,
Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
Richard Henderson <rth@twiddle.net>,
Chris Zankel <chris@zankel.net>,
Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
linux-parisc@vger.kernel.org,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
linux-mips@vger.kernel.org, linux-alpha@vger.kernel.org,
linuxppc-dev@lists.ozlabs.org,
"David S. Miller" <davem@davemloft.net>
Subject: Re: [RFC PATCH 6/7] serial: General support for multipoint addresses
Date: Sun, 6 Mar 2022 20:40:01 +0100 [thread overview]
Message-ID: <20220306194001.GD19394@wunner.de> (raw)
In-Reply-To: <20220302095606.14818-7-ilpo.jarvinen@linux.intel.com>
On Wed, Mar 02, 2022 at 11:56:05AM +0200, Ilpo Järvinen wrote:
> This patch adds generic support for serial multipoint
> addressing. Two new ioctls are added. TIOCSADDR is used to
Nit: "This patch adds..." is superfluous. Just write "Add ..."
in imperative mood.
> 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.
> [*] Technically, RS485 is just an electronic spec and does not
> itself specify the 9th bit addressing mode but 9th bit seems
> at least "semi-standard" way to do addressing with RS485.
Is 9th bit addressing actually used by an Intel customer or was
it implemented just for feature completeness? I think this mode
isn't used often (I've never seen a use case myself), primarily
because it requires disabling parity.
Thanks,
Lukas
WARNING: multiple messages have this Message-ID (diff)
From: Lukas Wunner <lukas@wunner.de>
To: "Ilpo Järvinen" <ilpo.jarvinen@linux.intel.com>
Cc: linux-serial@vger.kernel.org, Jiri Slaby <jirislaby@kernel.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
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>
Subject: Re: [RFC PATCH 6/7] serial: General support for multipoint addresses
Date: Sun, 6 Mar 2022 20:40:01 +0100 [thread overview]
Message-ID: <20220306194001.GD19394@wunner.de> (raw)
In-Reply-To: <20220302095606.14818-7-ilpo.jarvinen@linux.intel.com>
On Wed, Mar 02, 2022 at 11:56:05AM +0200, Ilpo Järvinen wrote:
> This patch adds generic support for serial multipoint
> addressing. Two new ioctls are added. TIOCSADDR is used to
Nit: "This patch adds..." is superfluous. Just write "Add ..."
in imperative mood.
> 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.
> [*] Technically, RS485 is just an electronic spec and does not
> itself specify the 9th bit addressing mode but 9th bit seems
> at least "semi-standard" way to do addressing with RS485.
Is 9th bit addressing actually used by an Intel customer or was
it implemented just for feature completeness? I think this mode
isn't used often (I've never seen a use case myself), primarily
because it requires disabling parity.
Thanks,
Lukas
next prev parent reply other threads:[~2022-03-06 19:40 UTC|newest]
Thread overview: 48+ 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 ` Ilpo Järvinen
2022-03-02 9:56 ` Ilpo Järvinen
2022-03-02 9:56 ` [RFC PATCH 6/7] serial: General support for multipoint addresses Ilpo Järvinen
2022-03-02 9:56 ` Ilpo Järvinen
2022-03-02 9:56 ` Ilpo Järvinen
2022-03-06 19:40 ` Lukas Wunner [this message]
2022-03-06 19:40 ` Lukas Wunner
2022-03-06 19:40 ` Lukas Wunner
2022-03-07 9:48 ` Ilpo Järvinen
2022-03-07 9:48 ` Ilpo Järvinen
2022-03-07 9:48 ` Ilpo Järvinen
2022-03-09 19:05 ` Lukas Wunner
2022-03-09 19:05 ` Lukas Wunner
2022-03-09 19:05 ` Lukas Wunner
2022-03-10 12:29 ` Ilpo Järvinen
2022-03-10 12:29 ` Ilpo Järvinen
2022-03-10 12:29 ` Ilpo Järvinen
2022-03-10 14:09 ` Andy Shevchenko
2022-03-10 14:09 ` Andy Shevchenko
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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