linux-kernel - Re: [PATCH 0/5] Add support for WD MyCloud EX2 Ultra (+ versatile UART-based restart/poweroff drivers)

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Message-ID: <20190723220628.GA13517@lunn.ch>
Date:   Wed, 24 Jul 2019 00:06:28 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     Evgeny Kolesnikov <evgenyz@...il.com>
Cc:     Mark Rutland <mark.rutland@....com>,
        Jason Cooper <jason@...edaemon.net>, linux-pm@...r.kernel.org,
        Gregory Clement <gregory.clement@...tlin.com>,
        Sebastian Reichel <sre@...nel.org>,
        linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
        Rob Herring <robh+dt@...nel.org>,
        linux-arm-kernel@...ts.infradead.org,
        Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>
Subject: Re: [PATCH 0/5] Add support for WD MyCloud EX2 Ultra (+ versatile
 UART-based restart/poweroff drivers)

On Tue, Jul 23, 2019 at 07:48:49PM +0200, Evgeny Kolesnikov wrote:
> On 23/07/2019 03:56, Andrew Lunn wrote:
> >On Mon, Jul 22, 2019 at 09:53:00PM +0200, Evgeny Kolesnikov wrote:
> >>
> >>The difference between uart-poweroff and qnap-poweroff is small, but important:
> >>uart-poweroff is able to send to an MCU a command of arbitrary length, and the command
> >>itself is defined in a DTS file for a specific device/board, thus making this driver
> >>applicable to wider range of devices.
> >
> >There is a lot of replicated code here, and in the original
> >qnap-poweroff.c driver. Please consolidate it by extending the current
> >driver. It should be easy to add a new compatible string, and turn
> >power_off_cfg.cmd into an array.
> 
> Hi, Andrew.
> 
> I've considered extending qnap driver, but I have some doubts about this
> approach.
> 
> First of all there is only a poweroff counterpart. As there is no
> qnap-restart driver, what should I do with uart-restart? Is it OK to have
> xxx-restart-poweroff driver (never saw anything like that)?

Hi Evgeny

There are a few options. You can refactor all the code into a library
and small drivers which wrap around the library. Or you can make the
driver handle both, using the compatible string to determine which it
should do.
 
> While I can add cmd as a parameter to qnap driver (having it converted
> into an array) it should be optional as original qnap relies on two
> hardcoded values for its devices.

That is not what i meant. You can make the current code more generic
by changing the single byte in power_off_cfg to an array. DT should
describe the hardware, not bytes you poke into registers. So it is
perfectly valid to have the bytes hard coded in the driver.

	  Andrew