linux-kernel - Re: [PATCH] net: mdio-gpio: support access that may sleep

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Message-ID: <553A7C73.7040002@cogentembedded.com>
Date:	Fri, 24 Apr 2015 20:25:07 +0300
From:	Sergei Shtylyov <sergei.shtylyov@...entembedded.com>
To:	Florian Fainelli <f.fainelli@...il.com>,
	David Miller <davem@...emloft.net>,
	vivien.didelot@...oirfairelinux.com
CC:	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	kernel@...oirfairelinux.com
Subject: Re: [PATCH] net: mdio-gpio: support access that may sleep

On 04/24/2015 06:56 PM, Florian Fainelli wrote:

>>> Some systems using mdio-gpio may use gpio on message based busses, which
>>> require sleeping (e.g. gpio from an I2C I/O expander).

>>> Since this driver does not use IRQ handler, it is safe to use the
>>> _cansleep suffixed gpio accessors.

>>> Signed-off-by: Vivien Didelot <vivien.didelot@...oirfairelinux.com>

>> Since this is down underneath the layer of an MII bus, you cannot
>> universally say that these routines are always called in a sleepable
>> context.

>> The PHY layer, and the driver itself above that, might call these
>> routines from timers, interruptes etc.

> The PHY library calls these routines from its state machine workqueue
> for that reason, or from process context (when invoked via ethtool
> ioctl). The only special case is phy_mac_interrupt() which is callable
> from interrupt context,

    It is not (as we have discussed recently) -- cancel_work_sync() may sleep.

WBR, Sergei

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