Re: [PATCH v2] serial: Deassert Transmit Enable on probe in driver-specific way

[Lukas Wunner <lukas@wunner.de>]

On Thu, Sep 22, 2022 at 06:06:56PM +0200, Greg Kroah-Hartman wrote:
> On Thu, Sep 22, 2022 at 05:43:53PM +0200, Lukas Wunner wrote:
> > On Thu, Sep 22, 2022 at 04:43:51PM +0200, Greg Kroah-Hartman wrote:
> > > On Wed, Sep 21, 2022 at 06:39:33AM +0200, Lukas Wunner wrote:
> > > > When a UART port is newly registered, uart_configure_port() seeks to
> > > > deassert RS485 Transmit Enable by setting the RTS bit in port->mctrl.
> > > > However a number of UART drivers interpret a set RTS bit as *assertion*
> > > > instead of deassertion:  Affected drivers include those using
> > > > serial8250_em485_config() (except 8250_bcm2835aux.c) and some using
> > > > mctrl_gpio (e.g. imx.c).
> > > > 
> > > > Since the interpretation of the RTS bit is driver-specific, it is not
> > > > suitable as a means to centrally deassert Transmit Enable in the serial
> > > > core.  Instead, the serial core must call on drivers to deassert it in
> > > > their driver-specific way.  One way to achieve that is to call
> > > > ->rs485_config().  It implicitly deasserts Transmit Enable.
> > > > 
> > > > So amend uart_configure_port() and uart_resume_port() to invoke
> > > > uart_rs485_config().  That allows removing calls to uart_rs485_config()
> > > > from drivers' ->probe() hooks and declaring the function static.
> > [...]
> > > 
> > > This message never made it to lore.kernel.org, so I can't seem to apply
> > > it using `b4`.
> > > 
> > > Can you resend it so that it does make it to the public archives?
> > 
> > Yes, both v1 and v2 didn't make it to the mailing list archive.
> > My suspicion is that the Cc: line was probably too long.
> > 
> > I resent as v3 with only you in To: and the mailing list in Cc: and
> > this time it went through:
> > 
> > https://lore.kernel.org/linux-serial/2de36eba3fbe11278d5002e4e501afe0ceaca039.1663860626.git.lukas@wunner.de/
> > 
> > On the bright side, v2 contained an embarrassing checkpatch issue
> > (superfluous newline) and resending as v3 provided a welcome
> > opportunity to fix that. :)
> 
> v3 did not have a changelog :(
> 
> v4?

Well, the changelog is above.  (Only the superfluous newline was removed
in v3 vis-à-vis v2.)

Here's a v4 with full changelog:

https://lore.kernel.org/linux-serial/2de36eba3fbe11278d5002e4e501afe0ceaca039.1663863805.git.lukas@wunner.de/