{"id":2229271,"url":"http://patchwork.ozlabs.org/api/1.1/patches/2229271/?format=json","web_url":"http://patchwork.ozlabs.org/project/linux-i2c/patch/20260427-i2c-xiic-v1-1-e6207f9aa5ad@nexthop.ai/","project":{"id":35,"url":"http://patchwork.ozlabs.org/api/1.1/projects/35/?format=json","name":"Linux I2C development","link_name":"linux-i2c","list_id":"linux-i2c.vger.kernel.org","list_email":"linux-i2c@vger.kernel.org","web_url":"","scm_url":"","webscm_url":""},"msgid":"<20260427-i2c-xiic-v1-1-e6207f9aa5ad@nexthop.ai>","date":"2026-04-28T00:18:06","name":"[1/3] i2c: xiic: preserve PEC byte length in SMBus block read setup","commit_ref":null,"pull_url":null,"state":"new","archived":false,"hash":"748b0bd904bc32f660048f518445ef8315b22973","submitter":{"id":92480,"url":"http://patchwork.ozlabs.org/api/1.1/people/92480/?format=json","name":"Abdurrahman Hussain via B4 Relay","email":"devnull+abdurrahman.nexthop.ai@kernel.org"},"delegate":null,"mbox":"http://patchwork.ozlabs.org/project/linux-i2c/patch/20260427-i2c-xiic-v1-1-e6207f9aa5ad@nexthop.ai/mbox/","series":[{"id":501748,"url":"http://patchwork.ozlabs.org/api/1.1/series/501748/?format=json","web_url":"http://patchwork.ozlabs.org/project/linux-i2c/list/?series=501748","date":"2026-04-28T00:18:06","name":"i2c: xiic: fix SMBus block read and PEC support","version":1,"mbox":"http://patchwork.ozlabs.org/series/501748/mbox/"}],"comments":"http://patchwork.ozlabs.org/api/patches/2229271/comments/","check":"pending","checks":"http://patchwork.ozlabs.org/api/patches/2229271/checks/","tags":{},"headers":{"Return-Path":"\n ","X-Original-To":["incoming@patchwork.ozlabs.org","linux-i2c@vger.kernel.org"],"Delivered-To":"patchwork-incoming@legolas.ozlabs.org","Authentication-Results":["legolas.ozlabs.org;\n\tdkim=pass (2048-bit key;\n unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256\n header.s=k20201202 header.b=FTZO1ACo;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=vger.kernel.org\n (client-ip=172.232.135.74; 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charset=\"utf-8\"","Content-Transfer-Encoding":"7bit","Message-Id":"<20260427-i2c-xiic-v1-1-e6207f9aa5ad@nexthop.ai>","References":"<20260427-i2c-xiic-v1-0-e6207f9aa5ad@nexthop.ai>","In-Reply-To":"<20260427-i2c-xiic-v1-0-e6207f9aa5ad@nexthop.ai>","To":"Michal Simek , Andi Shyti ","Cc":"linux-arm-kernel@lists.infradead.org, linux-i2c@vger.kernel.org,\n linux-kernel@vger.kernel.org, Abdurrahman Hussain ","X-Mailer":"b4 0.15.1","X-Developer-Signature":"v=1; a=openpgp-sha256; l=2279;\n i=abdurrahman@nexthop.ai; h=from:subject:message-id;\n bh=WbRNSgR6fF75ujIFRpZT+WIk0CWNPjAlMacuue3U6KE=;\n b=owJ4nJvAy8zAJbYltPXv6rsCXxhPqyUxZL7/c3B1ziaWhgZtFrFK/7l1X/ruSL6cYMDSVjL1j\n c2+ms//ngV2lLIwiHExyIopssx55P+mraMtYkPMIXuYOaxMIEMYuDgFYCJT7jAydHBtfsJ7Ujyo\n QjBN2L0pu0lRwTj1x/cph3/Ku6i+WVcWz/BPQZ3xXJja3qblId0ujyKkJq17U3jguKjB1QquM6I\n zzQ/zAgDNJ07Z","X-Developer-Key":"i=abdurrahman@nexthop.ai; a=openpgp;\n fpr=9CE24FEC86888658B05CC23FB45585FDABDD10F4","X-Endpoint-Received":"by B4 Relay for abdurrahman@nexthop.ai/default with\n auth_id=756","X-Original-From":"Abdurrahman Hussain ","Reply-To":"abdurrahman@nexthop.ai"},"content":"From: Abdurrahman Hussain \n\nxiic_smbus_block_read_setup() overwrites rx_msg->len based on the\nannounced block length byte, but the i2c core appends an extra byte to\nmsg->len when PEC is enabled on the client (see\n__i2c_smbus_xfer_emulated in i2c-core-smbus.c). Before this handler\nruns, rx_msg->len is therefore 1 + pec_len, where pec_len is 0 or 1.\n\nOverwriting rx_msg->len to rxmsg_len + 1 drops that PEC byte from the\ncaller's buffer: the PEC byte is never drained from the FIFO and the\ncore's i2c_smbus_check_pec() reads the last payload byte instead of\nthe actual PEC, returning -EBADMSG even on clean transfers. Capture\npec_len before the overwrite and add it back when recomputing\nrx_msg->len.\n\nThis is a pure bug fix; non-PEC behaviour is unchanged (pec_len == 0).\nTested on a Xilinx AXI IIC FPGA block driving an adm1266 PMBus\nblackbox read -- with PEC enabled the full 64-byte record transfers\ncleanly after this change.\n\nSigned-off-by: Abdurrahman Hussain \n---\n drivers/i2c/busses/i2c-xiic.c | 6 ++++--\n 1 file changed, 4 insertions(+), 2 deletions(-)","diff":"diff --git a/drivers/i2c/busses/i2c-xiic.c b/drivers/i2c/busses/i2c-xiic.c\nindex 3e7735e1dae0..959a47b645a5 100644\n--- a/drivers/i2c/busses/i2c-xiic.c\n+++ b/drivers/i2c/busses/i2c-xiic.c\n@@ -539,6 +539,8 @@ static void xiic_smbus_block_read_setup(struct xiic_i2c *i2c)\n \n \t/* Check if received length is valid */\n \tif (rxmsg_len <= I2C_SMBUS_BLOCK_MAX) {\n+\t\tunsigned int pec_len = i2c->rx_msg->len - 1;\n+\n \t\t/* Set Receive fifo depth */\n \t\tif (rxmsg_len > IIC_RX_FIFO_DEPTH) {\n \t\t\t/*\n@@ -546,7 +548,7 @@ static void xiic_smbus_block_read_setup(struct xiic_i2c *i2c)\n \t\t\t * Receive fifo depth should set to Rx fifo capacity minus 1\n \t\t\t */\n \t\t\trfd_set = IIC_RX_FIFO_DEPTH - 1;\n-\t\t\ti2c->rx_msg->len = rxmsg_len + 1;\n+\t\t\ti2c->rx_msg->len = rxmsg_len + 1 + pec_len;\n \t\t} else if ((rxmsg_len == 1) ||\n \t\t\t(rxmsg_len == 0)) {\n \t\t\t/*\n@@ -562,7 +564,7 @@ static void xiic_smbus_block_read_setup(struct xiic_i2c *i2c)\n \t\t\t * Receive fifo depth should set to Rx msg len minus 2\n \t\t\t */\n \t\t\trfd_set = rxmsg_len - 2;\n-\t\t\ti2c->rx_msg->len = rxmsg_len + 1;\n+\t\t\ti2c->rx_msg->len = rxmsg_len + 1 + pec_len;\n \t\t}\n \t\txiic_setreg8(i2c, XIIC_RFD_REG_OFFSET, rfd_set);\n \n","prefixes":["1/3"]}