From: slash.tmp@free•fr (Mason)
To: linux-arm-kernel@lists•infradead.org
Subject: Platform-specific suspend/resume code in drivers
Date: Wed, 8 Jun 2016 18:26:30 +0200 [thread overview]
Message-ID: <57584736.7020201@free.fr> (raw)
In-Reply-To: <Pine.LNX.4.44L0.1606071055010.1604-100000@iolanthe.rowland.org>
On 07/06/2016 17:06, Alan Stern wrote:
> On Tue, 7 Jun 2016, Mason wrote:
>
>> Another point of confusion for me is this: drivers are supposed to
>> be shared among platforms, right? So my platform-specific suspend
>> code should be enabled only if my platform is detected at run-time?
>
> Is your device platform-specific? If it is then the driver is also
> platform-specific, and so no part of the driver will be called at
> runtime unless your platform is detected.
Specifically, my platform uses
drivers/net/ethernet/aurora/nb8800.c => 3 entries in of_match_table.
drivers/tty/serial/8250/8250_core.c (CONFIG_SERIAL_8250_RT288X variant)
and also the XHCI USB3 driver, and AHCI SATA driver, wouldn't I need to
save the context for these too?
> If the device isn't platform-specific then the driver has to work on a
> bunch of different platforms. It should be written to be
> platform-independent as much as possible.
>
>> So this means I need to add in the probe function, for every driver
>> my platform uses:
>>
>> if (platform == MY_PLATFORM) {
>> ops.suspend = my_suspend;
>> ops.resume = my_resume;
>> }
>>
>> Is that correct?
>
> No. For one thing, you only have to worry about the
> platform-independent drivers -- you know that the platform-specific
> ones won't get used unless your platform is present.
I guess the thermal driver is platform-specific, but most devices
are third-party IP blocks, so there is a "common" driver upstream.
But I would need a platform-specific suspend/resume sequence,
just for my platform.
> For another, the driver should be written in a way that doesn't require
> this sort of code. The ops pointer (not any of the structure's members
> -- a pointer to the structure) should be set by the platform-dependent
> part of the driver that handles initialization.
I don't understand. If my platform loses context on suspend, then
I must save/restore it. But this wasteful operation should not be
imposed on other platforms.
Regards.
next prev parent reply other threads:[~2016-06-08 16:26 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-06-07 8:56 Platform-specific suspend/resume code in drivers Mason
2016-06-07 15:06 ` Alan Stern
2016-06-08 16:26 ` Mason [this message]
2016-06-08 17:45 ` Alan Stern
2016-06-08 21:26 ` Mason
2016-06-09 15:05 ` Alan Stern
2016-06-10 11:03 ` Mason
2016-06-10 14:19 ` Alan Stern
2016-06-10 22:32 ` Kevin Hilman
2016-06-10 13:39 ` Geert Uytterhoeven
2016-06-09 8:52 ` Sebastian Frias
2016-06-09 15:14 ` Alan Stern
2016-06-18 14:35 ` Pavel Machek
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