On 16. 06. 22, 7:04, Ilpo Järvinen wrote:
On Wed, 15 Jun 2022, Andy Shevchenko wrote:
On Wed, Jun 15, 2022 at 03:48:28PM +0300, Ilpo Järvinen wrote:
Add support for RS-485 multipoint addressing using 9th bit [*]. The
addressing mode is configured through .rs485_config().
ADDRB in termios indicates 9th bit addressing mode is enabled. In this
mode, 9th bit is used to indicate an address (byte) within the
communication line. ADDRB can only be enabled/disabled through
.rs485_config() that is also responsible for setting the destination and
receiver (filter) addresses.
[*] 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.
Cc: Arnd Bergmann <arnd@xxxxxxxx>
Cc: Jonathan Corbet <corbet@xxxxxxx>
Cc: linux-api@xxxxxxxxxxxxxxx
Cc: linux-doc@xxxxxxxxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
Cc: linux-arch@xxxxxxxxxxxxxxx
Hmm... In order to reduce commit messages you can move these Cc:s after the
cutter line ('---').
Ok, although the toolchain I use didn't support preserving --- content
so I had to create hack to preserve them, hopefully nothing backfires due
to the hack. :-)
- __u32 padding[5]; /* Memory is cheap, new structs
- are a royal PITA .. */
+ __u8 addr_recv;
+ __u8 addr_dest;
+ __u8 padding[2 + 4 * sizeof(__u32)]; /* Memory is cheap, new structs
+ * are a royal PITA .. */
I'm not sure it's an equivalent. I would leave u32 members untouched, so
something like
__u8 addr_recv;
__u8 addr_dest;
__u8 padding0[2]; /* Memory is cheap, new structs
__u32 padding1[4]; * are a royal PITA .. */
And repeating about `pahole` tool which may be useful here to check for ABI
potential changes.
I cannot take __u32 padding[] away like that, this is an uapi header.
Yeah, but it's padding after all. I would personally break it for
example as Andy suggests (if pahole shows no differences in size on both
32/64 bit) and wait if something breaks. To be honest, I'd not expect
anyone to touch it. And if someone does, we would fix it somehow and
they should too...
thanks,
--
js
suse labs
