From: Viresh Kumar <viresh.kumar@linaro.org>
To: Vincent Whitchurch <vincent.whitchurch@axis.com>
Cc: "Chen, Conghui" <conghui.chen@intel.com>,
"Deng, Jie" <jie.deng@intel.com>,
Greg KH <gregkh@linuxfoundation.org>,
Wolfram Sang <wsa@kernel.org>,
"virtualization@lists.linux-foundation.org"
<virtualization@lists.linux-foundation.org>,
"linux-i2c@vger.kernel.org" <linux-i2c@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
kernel <kernel@axis.com>
Subject: Re: [PATCH 1/2] i2c: virtio: disable timeout handling
Date: Tue, 9 Nov 2021 10:22:21 +0530 [thread overview]
Message-ID: <20211109045221.xd6apt473jannag2@vireshk-i7> (raw)
In-Reply-To: <20211103144241.GA27285@axis.com>
On 03-11-21, 15:42, Vincent Whitchurch wrote:
> The suggested timeout is not meant to take into account the overhead of
> virtualization, but to be used by the virtio device as a timeout for the
> transaction on the I2C bus (presumably by programming this value to the
> physical I2C controller, if one exists).
>
> Assume that userspace (or an I2C client driver) asks for a timeout of 20
> ms for a particular transfer because it, say, knows that the particular
> connected I2C peripheral either responds within 10 ms to a particular
> register read or never responds, so it doesn't want to waste time
> waiting unnecessarily long for the transfer to complete.
>
> If the virtio device end does not have any information on what timeout
> is required (as in the current spec), it must assume some high value
> which will never cause I2C transactions to spuriously timeout, say 10
> seconds.
>
> Even if the virtio driver is fixed to copy and hold all buffers to avoid
> memory corruption and to time out and return to the caller after the
> requested 20 ms, the next I2C transfer can not be issued until 10
> seconds have passed, since the virtio device end will still be waiting
> for the hardcoded 10 second timeout and may not respond to new requests
> until that transfer has timed out.
Okay, so this is more about making sure the device times-out before
the driver or lets say in an expected time-frame. That should be okay
I guess.
--
viresh
next prev parent reply other threads:[~2021-11-09 4:52 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-19 7:46 [PATCH 0/2] virtio-i2c: Fix buffer handling Vincent Whitchurch
2021-10-19 7:46 ` [PATCH 1/2] i2c: virtio: disable timeout handling Vincent Whitchurch
2021-10-19 8:09 ` Viresh Kumar
2021-10-19 9:36 ` Greg KH
2021-10-19 9:42 ` Viresh Kumar
2021-10-19 11:15 ` Wolfram Sang
2021-10-19 14:14 ` Viresh Kumar
2021-10-19 11:16 ` Greg KH
2021-10-19 14:37 ` Viresh Kumar
2021-10-19 18:14 ` Wolfram Sang
2021-10-20 4:20 ` Jie Deng
2021-10-20 5:36 ` Greg KH
2021-10-20 6:35 ` Jie Deng
2021-10-20 6:41 ` Viresh Kumar
2021-10-20 7:04 ` Jie Deng
2021-10-20 10:55 ` Vincent Whitchurch
2021-10-20 11:03 ` Viresh Kumar
2021-10-21 3:30 ` Jie Deng
2021-10-29 12:24 ` Vincent Whitchurch
2021-11-01 5:23 ` Jie Deng
2021-11-03 6:18 ` Chen, Conghui
2021-11-03 6:37 ` Viresh Kumar
2021-11-03 14:42 ` Vincent Whitchurch
2021-11-09 4:52 ` Viresh Kumar [this message]
2021-10-20 3:36 ` Jie Deng
2021-10-19 7:46 ` [PATCH 2/2] i2c: virtio: fix completion handling Vincent Whitchurch
2021-10-19 8:22 ` Viresh Kumar
2021-10-20 8:54 ` Jie Deng
2021-10-20 9:17 ` Viresh Kumar
2021-10-20 10:38 ` Vincent Whitchurch
2021-10-20 10:47 ` Viresh Kumar
2021-10-29 11:54 ` Vincent Whitchurch
2021-10-21 5:55 ` Jie Deng
2021-10-21 5:58 ` Viresh Kumar
2021-11-02 4:32 ` Viresh Kumar
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