From: Wolfram Sang <wsa@kernel.org>
To: Sultan Alsawaf <sultan@kerneltoast.com>
Cc: linux-i2c@vger.kernel.org, jikos@kernel.org,
aaron.ma@canonical.com, admin@kryma.net,
andriy.shevchenko@linux.intel.com, benjamin.tissoires@redhat.com,
hdegoede@redhat.com, hn.chen@weidahitech.com,
jarkko.nikula@linux.intel.com, kai.heng.feng@canonical.com,
linux-input@vger.kernel.org, linux-kernel@vger.kernel.org,
mika.westerberg@linux.intel.com, vicamo.yang@canonical.com
Subject: Re: [PATCH v2 3/4] i2c: designware: Allow SMBus block reads up to 255 bytes in length
Date: Thu, 17 Sep 2020 22:57:04 +0200 [thread overview]
Message-ID: <20200917205704.GA18027@kunai> (raw)
In-Reply-To: <20200917052256.5770-4-sultan@kerneltoast.com>
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On Wed, Sep 16, 2020 at 10:22:55PM -0700, Sultan Alsawaf wrote:
> From: Sultan Alsawaf <sultan@kerneltoast.com>
>
> According to the SMBus 3.0 protocol specification, block transfer limits
> were increased from 32 bytes to 255 bytes. Remove the obsolete 32-byte
> limitation.
Sadly, it is not that easy. We are trying to extend BLOCK_MAX to 255
(SMBus 3 specs) but there are various things to be considered,
especially with buffers and when passing it to userspace. Check here for
the discussion (and you are welcome to join, of course):
http://patchwork.ozlabs.org/project/linux-i2c/list/?submitter=79741&state=*
>
> Signed-off-by: Sultan Alsawaf <sultan@kerneltoast.com>
> ---
> drivers/i2c/busses/i2c-designware-master.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/i2c/busses/i2c-designware-master.c b/drivers/i2c/busses/i2c-designware-master.c
> index 22f28516bca7..5bd64bd17d94 100644
> --- a/drivers/i2c/busses/i2c-designware-master.c
> +++ b/drivers/i2c/busses/i2c-designware-master.c
> @@ -433,7 +433,7 @@ i2c_dw_read(struct dw_i2c_dev *dev)
> regmap_read(dev->map, DW_IC_DATA_CMD, &tmp);
> if (flags & I2C_M_RECV_LEN) {
> /* Ensure length byte is a valid value */
> - if (tmp <= I2C_SMBUS_BLOCK_MAX && tmp > 0)
> + if (tmp > 0)
> len = i2c_dw_recv_len(dev, tmp);
> else
> len = i2c_dw_recv_len(dev, len);
> --
> 2.28.0
>
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next prev parent reply other threads:[~2020-09-17 20:57 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-17 5:22 [PATCH v2 0/4] i2c-hid: Save power by reducing i2c xfers with block reads Sultan Alsawaf
2020-09-17 5:22 ` [PATCH v2 1/4] i2c: designware: Fix transfer failures for invalid SMBus " Sultan Alsawaf
2020-09-17 5:22 ` [PATCH v2 2/4] i2c: designware: Ensure tx_buf_len is nonzero for " Sultan Alsawaf
2020-09-17 12:47 ` Andy Shevchenko
2020-09-17 13:44 ` Jarkko Nikula
2020-09-17 14:45 ` Andy Shevchenko
2020-09-17 5:22 ` [PATCH v2 3/4] i2c: designware: Allow SMBus block reads up to 255 bytes in length Sultan Alsawaf
2020-09-17 20:57 ` Wolfram Sang [this message]
2020-09-17 23:12 ` Sultan Alsawaf
2020-09-17 5:22 ` [PATCH v2 4/4] HID: i2c-hid: Use block reads when possible to save power Sultan Alsawaf
2020-09-17 14:02 ` [PATCH v2 0/4] i2c-hid: Save power by reducing i2c xfers with block reads Andy Shevchenko
2020-09-23 13:59 ` Jarkko Nikula
2020-09-22 9:19 ` Jiri Kosina
2020-09-22 11:36 ` Wolfram Sang
2020-09-22 19:59 ` Jiri Kosina
2020-09-23 6:02 ` Sultan Alsawaf
2020-10-16 11:16 ` Hans de Goede
2020-10-16 15:24 ` Sultan Alsawaf
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