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Date: Tue, 02 Nov 2010 08:30:08 +0200 From: Onkalo Samu <samu.p.onkalo@...ia.com> To: ext Alan Cox <alan@...ux.intel.com> Cc: Ming Lei <tom.leiming@...il.com>, "gregkh@...e.de" <gregkh@...e.de>, "hmh@....eng.br" <hmh@....eng.br>, "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org> Subject: Re: [RFC PATCH] device-core: sysfs open - close notify On Mon, 2010-11-01 at 18:11 +0100, ext Alan Cox wrote: > > Your patch may cause many unnecessary memory waste because > > most of drivers does not need attribute file .open/.close notifier. > > Firstly there are not that many driver objects in a small system so it > wouldn't take that much to shift the balance the other way. Secondly > its becoming clear that every time a driver goes to runtime pm these > issues come up - even with things like configuration values for drivers > that need to wake the hardware and then silence it. > > So the whole sysfs/open thing is going to keep haunting us with runtime > pm, the question is where to put the callbacks so we don't bloat stuff. > Clearly not per attribute or per sysfs node. One possibility would be > with the runtime pm stuff, but that would need a clean reliable way to > go sysfs->device->runtime_pm > > There are also obvious hackish ways to handle it like passing a 0 > length read to indicate close etc - they save memory but they are > asking for problems in future. > Memory footprint could be minimized by combining separate open close functions to one like sysfs_open_close_notify and the actual operation would be a call parameter. But is that hackish? And perhaps some flags could be used to indicate which attributes trigs the open / close notification. -Samu -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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