linux-kernel - Re: [PATCH V15 3/6] i2c: tegra: fix maximum transfer size

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Date:   Fri, 8 Feb 2019 15:46:50 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Sowjanya Komatineni <skomatineni@...dia.com>,
        thierry.reding@...il.com, jonathanh@...dia.com,
        mkarthik@...dia.com, smohammed@...dia.com, talho@...dia.com
Cc:     linux-tegra@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-i2c@...r.kernel.org
Subject: Re: [PATCH V15 3/6] i2c: tegra: fix maximum transfer size

08.02.2019 1:25, Dmitry Osipenko пишет:
>> 08.02.2019 1:16, Sowjanya Komatineni пишет:> 
>>>> This is wrong, 65535 = 64 * 1024 - 1.
>>>>
>>>> Let's just use size-constants provided by kernel:
>>>>
>>>> static const struct i2c_adapter_quirks tegra_i2c_quirks = {
>>>> 	.flags = I2C_AQ_NO_ZERO_LEN,
>>>> 	.max_read_len = SZ_4K,
>>>> 	.max_write_len = SZ_4K - I2C_PACKET_HEADER_SIZE, };
>>>>
>>>> static const struct i2c_adapter_quirks tegra194_i2c_quirks = {
>>>> 	.flags = I2C_AQ_NO_ZERO_LEN,
>>>> 	.max_read_len = SZ_64K,
>>>> 	.max_write_len = SZ_64K - I2C_PACKET_HEADER_SIZE, };
>>>>
>>>>
>>>> I'll take a look at other patches later today, no need to send out new version right now.
>>>>
>>>>
>>>
>>> SIZE_64K is 0x00010000 (65536)
>>>
>>> msg len is u16 and max that can be set to msg.len is 65535
> 
> Ah, okay. Then it looks about right, maybe it's time to change u16 to u32 in the I2C core.
> 

Here is my suggestion:

1) Use SZ_4K / SZ_64K that I suggested above.

2) Squash this patch into the DMA-patch.

3) Add another patch (before the DMA-patch) that changes max_read_len/max_write_len types to u32 in the include/linux/i2c.h