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SubjectRe: [PATCH 2/3] hwmon: (occ) Remove sequence numbering and checksum calculation
On Fri, 16 Jul 2021 at 15:19, Eddie James <eajames@linux.ibm.com> wrote:
>
> Checksumming of the request and sequence numbering is now done in the
> OCC interface driver in order to keep unique sequence numbers. So
> remove those in the hwmon driver.
>
> Signed-off-by: Eddie James <eajames@linux.ibm.com>
> ---
> drivers/hwmon/occ/common.c | 30 ++++++++++++------------------
> drivers/hwmon/occ/common.h | 3 +--
> drivers/hwmon/occ/p8_i2c.c | 15 +++++++++------
> drivers/hwmon/occ/p9_sbe.c | 4 ++--
> 4 files changed, 24 insertions(+), 28 deletions(-)
>
> diff --git a/drivers/hwmon/occ/common.c b/drivers/hwmon/occ/common.c
> index 0d68a78be980..fc298268c89e 100644
> --- a/drivers/hwmon/occ/common.c
> +++ b/drivers/hwmon/occ/common.c
> @@ -132,22 +132,20 @@ struct extended_sensor {
> static int occ_poll(struct occ *occ)
> {
> int rc;
> - u16 checksum = occ->poll_cmd_data + occ->seq_no + 1;
> - u8 cmd[8];
> + u8 cmd[7];

The shortening of the command seems unrelated?

If you leave it at 8 then you avoid the special casing below. Is there
any downside to sending the extra 0 byte at the end?

> struct occ_poll_response_header *header;
>
> /* big endian */
> - cmd[0] = occ->seq_no++; /* sequence number */
> + cmd[0] = 0; /* sequence number */
> cmd[1] = 0; /* cmd type */
> cmd[2] = 0; /* data length msb */
> cmd[3] = 1; /* data length lsb */
> cmd[4] = occ->poll_cmd_data; /* data */
> - cmd[5] = checksum >> 8; /* checksum msb */
> - cmd[6] = checksum & 0xFF; /* checksum lsb */
> - cmd[7] = 0;
> + cmd[5] = 0; /* checksum msb */
> + cmd[6] = 0; /* checksum lsb */

> --- a/drivers/hwmon/occ/p8_i2c.c> +++ b/drivers/hwmon/occ/p8_i2c.c
> @@ -97,18 +97,21 @@ static int p8_i2c_occ_putscom_u32(struct i2c_client *client, u32 address,
> }
>
> static int p8_i2c_occ_putscom_be(struct i2c_client *client, u32 address,
> - u8 *data)
> + u8 *data, size_t len)
> {
> - __be32 data0, data1;
> + __be32 data0 = 0, data1 = 0;
>
> - memcpy(&data0, data, 4);
> - memcpy(&data1, data + 4, 4);
> + memcpy(&data0, data, min(len, 4UL));

The UL here seems unnecessary (and dropping it should fix your 0day
bot warnings).

But I think it would be simpler to go back to a fixed length of 8.

> + if (len > 4UL) {
> + len -= 4;
> + memcpy(&data1, data + 4, min(len, 4UL));
> + }
>
> return p8_i2c_occ_putscom_u32(client, address, be32_to_cpu(data0),
> be32_to_cpu(data1));
> }

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