linux-kernel - Re: [PATCH v6] i2c: virtio: add a virtio i2c frontend driver

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Message-ID: <a3d4ce55-db25-5f96-ff44-5b76edfe9e08@redhat.com>
Date:   Wed, 10 Mar 2021 11:59:09 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     Jie Deng <jie.deng@...el.com>, linux-i2c@...r.kernel.org,
        virtualization@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org
Cc:     mst@...hat.com, wsa@...nel.org, wsa+renesas@...g-engineering.com,
        andriy.shevchenko@...ux.intel.com, conghui.chen@...el.com,
        arnd@...db.de, kblaiech@...lanox.com,
        jarkko.nikula@...ux.intel.com, Sergey.Semin@...kalelectronics.ru,
        rppt@...nel.org, loic.poulain@...aro.org, tali.perry1@...il.com,
        u.kleine-koenig@...gutronix.de, bjorn.andersson@...aro.org,
        yu1.wang@...el.com, shuo.a.liu@...el.com, viresh.kumar@...aro.org,
        stefanha@...hat.com, pbonzini@...hat.com
Subject: Re: [PATCH v6] i2c: virtio: add a virtio i2c frontend driver


On 2021/3/10 10:22 上午, Jie Deng wrote:
>
> On 2021/3/4 17:15, Jason Wang wrote:
>>
>>
>>> +        }
>>> +
>>> +        if (msgs[i].flags & I2C_M_RD)
>>> +            memcpy(msgs[i].buf, req->buf, msgs[i].len);
>>
>>
>> Sorry if I had asked this before but any rason not to use msg[i].buf 
>> directly?
>>
>>
> The msg[i].buf is passed by the I2C core. I just noticed that these 
> bufs are not
> always allocated by kmalloc. They may come from the stack, which may 
> cause
> the check "sg_init_one -> sg_set_buf -> virt_addr_valid"  to fail. 
> Therefore the
> msg[i].buf is not suitable for direct use here.
>
> Regards.


Right, stack is virtually mapped.

Thanks