From: Jarkko Nikula <jarkko.nikula@linux.intel.com>
To: Sultan Alsawaf <sultan@kerneltoast.com>,
Aaron Ma <aaron.ma@canonical.com>,
Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
Benjamin Tissoires <benjamin.tissoires@redhat.com>,
Hans de Goede <hdegoede@redhat.com>,
HungNien Chen <hn.chen@weidahitech.com>,
Jiri Kosina <jikos@kernel.org>,
Kai-Heng Feng <kai.heng.feng@canonical.com>,
linux-i2c@vger.kernel.org, linux-input@vger.kernel.org,
linux-kernel@vger.kernel.org,
Mika Westerberg <mika.westerberg@linux.intel.com>,
Pavel Balan <admin@kryma.net>, Tin Huynh <tnhuynh@apm.com>,
Wolfram Sang <wsa@kernel.org>,
You-Sheng Yang <vicamo.yang@canonical.com>
Subject: Re: [PATCH 1/2] i2c: designware: Only check the first byte for SMBus block read length
Date: Tue, 16 Jun 2020 16:22:30 +0300 [thread overview]
Message-ID: <9782f44e-4e01-4e5d-cc50-ab9e2219085c@linux.intel.com> (raw)
In-Reply-To: <20200614210255.4641-2-sultan@kerneltoast.com>
On 6/15/20 12:02 AM, Sultan Alsawaf wrote:
> From: Sultan Alsawaf <sultan@kerneltoast.com>
>
> SMBus block reads can be broken because the read function will just skip
> over bytes it doesn't like until reaching a byte that conforms to the
> length restrictions for block reads. This is problematic when it isn't
> known if the incoming payload is indeed a conforming block read.
>
> According to the SMBus specification, block reads will only send the
> payload length in the first byte, so we can fix this by only considering
> the first byte in a sequence for block read length purposes.
>
> Fixes: c3ae106050b9 ("i2c: designware: Implement support for SMBus block read and write")
> Signed-off-by: Sultan Alsawaf <sultan@kerneltoast.com>
> ---
> drivers/i2c/busses/i2c-designware-master.c | 10 +++++-----
> 1 file changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/i2c/busses/i2c-designware-master.c b/drivers/i2c/busses/i2c-designware-master.c
> index d6425ad6e6a3..16d38b8fc19a 100644
> --- a/drivers/i2c/busses/i2c-designware-master.c
> +++ b/drivers/i2c/busses/i2c-designware-master.c
> @@ -398,7 +398,6 @@ i2c_dw_recv_len(struct dw_i2c_dev *dev, u8 len)
> len += (flags & I2C_CLIENT_PEC) ? 2 : 1;
> dev->tx_buf_len = len - min_t(u8, len, dev->rx_outstanding);
> msgs[dev->msg_read_idx].len = len;
> - msgs[dev->msg_read_idx].flags &= ~I2C_M_RECV_LEN;
>
> return len;
> }
Please update the comment about masking the flag a few lines above this
change.
> @@ -430,10 +429,11 @@ i2c_dw_read(struct dw_i2c_dev *dev)
> u32 flags = msgs[dev->msg_read_idx].flags;
>
> regmap_read(dev->map, DW_IC_DATA_CMD, &tmp);
> - /* Ensure length byte is a valid value */
> - if (flags & I2C_M_RECV_LEN &&
> - tmp <= I2C_SMBUS_BLOCK_MAX && tmp > 0) {
> - len = i2c_dw_recv_len(dev, tmp);
> + if (flags & I2C_M_RECV_LEN) {
> + /* Ensure length byte is a valid value */
> + if (tmp <= I2C_SMBUS_BLOCK_MAX && tmp > 0)
> + len = i2c_dw_recv_len(dev, tmp);
> + msgs[dev->msg_read_idx].flags &= ~I2C_M_RECV_LEN;
> }
> *buf++ = tmp;
> dev->rx_outstanding--;
With above comment change this looks good to me.
--
Jarkko
next prev parent reply other threads:[~2020-06-16 13:22 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-14 21:02 [PATCH 0/2] i2c-hid: Save power by reducing i2c xfers with block reads Sultan Alsawaf
2020-06-14 21:02 ` [PATCH 1/2] i2c: designware: Only check the first byte for SMBus block read length Sultan Alsawaf
2020-06-15 9:40 ` Andy Shevchenko
2020-06-15 16:03 ` Sultan Alsawaf
2020-06-15 16:07 ` Andy Shevchenko
2020-06-15 17:15 ` Sultan Alsawaf
2020-06-16 13:22 ` Jarkko Nikula [this message]
2020-06-16 15:43 ` [PATCH v2] " Sultan Alsawaf
2020-06-17 11:08 ` Jarkko Nikula
2020-06-14 21:02 ` [PATCH 2/2] HID: i2c-hid: Use block reads when possible to save power Sultan Alsawaf
2020-06-16 13:43 ` Jarkko Nikula
2020-06-16 15:49 ` [PATCH v2] " Sultan Alsawaf
2020-06-16 16:41 ` Andy Shevchenko
2020-06-16 17:18 ` Andi Shyti
2020-06-16 17:32 ` Sultan Alsawaf
2020-06-16 18:02 ` Andi Shyti
2020-06-16 18:17 ` Sultan Alsawaf
2020-06-17 11:17 ` Jarkko Nikula
2020-06-29 17:43 ` Sultan Alsawaf
2020-07-01 8:04 ` Jarkko Nikula
2020-07-01 15:00 ` Sultan Alsawaf
2020-07-03 11:18 ` Jarkko Nikula
2020-09-14 0:15 ` [PATCH v3] i2c: Squash of SMBus block read patchset " Sultan Alsawaf
[not found] ` <bcf9cd02-13d1-8f87-8ef9-2f05f0b54808@linux.intel.com>
2020-09-15 17:48 ` Sultan Alsawaf
2020-09-16 14:09 ` Jarkko Nikula
2020-09-15 20:44 ` Jiri Kosina
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