From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtpout-02.galae.net (smtpout-02.galae.net [185.246.84.56]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 373642D6E55 for ; Tue, 27 Jan 2026 09:26:03 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=185.246.84.56 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769505964; cv=none; b=aQxhtO/JeoAvzbgWucFpqTdJ0MO11guV3N+sjH8aI5ZIDxkdijb4lFA4BpLga9EkcYcDe55C7LhofYdNvS7CiVKF2zR1iwYVzvrAf30RVM/NAWxHRo+HiUWXOTN2o+EkxefNEF+Gw5o2Iwk8k1lcBwWag/ghoo2rw1ZpX1a2FQQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769505964; c=relaxed/simple; bh=pkAH9sZLqQgxEtbfYDwO1eAuCAW3IVC4KBCXcqpGRe4=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=d/9ArPGRMyjZhJBVBYg1+vhVv36P5Z52S3NDiCHOede2Rtit3rhXNN5cciPsAgMZgGB5wm4ACjjoGBEm6e763S6E4XGxuhj+WNR6c/dq70yCg4GsM1NFz5OXvmSgrr0zUM6FG58M7jgxUvLeOF5goEo889j3USwojdXJFwxHyJA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=bootlin.com; spf=pass smtp.mailfrom=bootlin.com; dkim=pass (2048-bit key) header.d=bootlin.com header.i=@bootlin.com header.b=DWPcRq/F; arc=none smtp.client-ip=185.246.84.56 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=bootlin.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=bootlin.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=bootlin.com header.i=@bootlin.com header.b="DWPcRq/F" Received: from smtpout-01.galae.net (smtpout-01.galae.net [212.83.139.233]) by smtpout-02.galae.net (Postfix) with ESMTPS id A96F41A2A6C; Tue, 27 Jan 2026 09:26:01 +0000 (UTC) Received: from mail.galae.net (mail.galae.net [212.83.136.155]) by smtpout-01.galae.net (Postfix) with ESMTPS id 7F2BB606F5; Tue, 27 Jan 2026 09:26:01 +0000 (UTC) Received: from [127.0.0.1] (localhost [127.0.0.1]) by localhost (Mailerdaemon) with ESMTPSA id 8571C119A8683; Tue, 27 Jan 2026 10:26:00 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bootlin.com; s=dkim; t=1769505961; h=from:subject:date:message-id:to:cc:mime-version:content-type: content-transfer-encoding:in-reply-to:references; bh=zPB1Ge6vulCmfr4sqT06S6djlJ24muffY5hjqSMtGrA=; b=DWPcRq/FZ/Rl48j2ecKgXXttdk1SfYM5SuHFflM+J4k4gf1SRfq02zpbkC1dMwP0HKs2aj Yp+wX6nVWJON4MV7mMNlzt82JEeBoSy0tMfBUZn64S2hLLMhO23j6NrAsP75kK6b9Vcwkr lNvnePvgr3xqp/cBj7t9Be09msB5I+c8T5C6dfSJAAeNSjsrQxTSxiQmcB0M+Nhk1Dh6mN K8kycjyXEdqLaZcYbKmbNTkLn2ahMeUTmV8UyJ5kxahZWnA8K9Vkhzjk/LtNp/jtEdic3J RYF4OnzMFEIXx9zQXir12Kd4v4VtbD6oatH+1/mR0bw0kiEhVbE63qN9lVhqGQ== From: =?utf-8?q?Beno=C3=AEt_Monin?= Date: Tue, 27 Jan 2026 10:25:58 +0100 Subject: [PATCH i2c-tools v3 2/2] i2ctransfer: Add optional message modifier flags Precedence: bulk X-Mailing-List: linux-i2c@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 8bit Message-Id: <20260127-msg-flags-v3-2-e7539945db2b@bootlin.com> References: <20260127-msg-flags-v3-0-e7539945db2b@bootlin.com> In-Reply-To: <20260127-msg-flags-v3-0-e7539945db2b@bootlin.com> To: linux-i2c@vger.kernel.org Cc: Jean Delvare , Wolfram Sang , Thomas Petazzoni , =?utf-8?q?Beno=C3=AEt_Monin?= X-Mailer: b4 0.14.3 X-Last-TLS-Session-Version: TLSv1.3 Allow setting protocol mangling and repeated start elision flags of an i2c message with a set of optional command-line flags. These optional flags are parsed at the beginning of the DESC field up to a read or write flag. For example, to read one byte from address 0x50 followed by a stop, then write two bytes at 0x54 on bus 0, one would call i2ctransfer as follow: i2ctransfer 0 pr1@0x50 w2@0x54 0x10 0x20 Since the new flags are optional, this patch preserves the compatibility of the i2ctransfer syntax. Handling of the message flags is done in add_flag_if_supported(). This function checks if the flag is defined at compile time and if the adapter supports the required functionality to handle the flag. Signed-off-by: Benoît Monin --- tools/i2ctransfer.8 | 28 ++++++++++++- tools/i2ctransfer.c | 119 ++++++++++++++++++++++++++++++++++++++++++++++------ 2 files changed, 133 insertions(+), 14 deletions(-) diff --git a/tools/i2ctransfer.8 b/tools/i2ctransfer.8 index 4bdf436..ca41241 100644 --- a/tools/i2ctransfer.8 +++ b/tools/i2ctransfer.8 @@ -96,8 +96,11 @@ The number of blocks is limited by the Linux Kernel and defined by I2C_RDWR_IOCT .I desc blocks are composed like this: -.I {r|w}[@address] +.I [inpst]{r|w}[@address] +.TP +.B [inpst] +If supported, specifies optional MESSAGE MODIFIER FLAGS. See the section below for details. .TP .B {r|w} specifies if the message is read or write @@ -141,6 +144,29 @@ decrease value by 1 until end of message (i.e. 0xff- means 0xff, 0xfe, 0xfd, ... p use value as seed for an 8 bit pseudo random sequence (i.e. 0p means 0x00, 0x50, 0xb0, ...) +.SH "MESSAGE MODIFIER FLAGS" +.PP +These optional flags can be used to change the handling of a message when it is sent on the bus. +They allow you to deviate from the I2C standard to work around device issues. +They should be used with care, as they can confuse your I2C bus. +Note that not all flags (or any) may be supported by your particular hardware and your kernel version. + +.TP +.B i +ignore NACK from client, treat them as ACK. +.TP +.B n +in a read message, master ACK/NACK bit is skipped. +.TP +.B p +emit a STOP after the message. +.TP +.B s +skip repeated start. +.TP +.B t +toggle read/write bit. + .SH EXAMPLES .PP On bus 0, from an EEPROM at address 0x50, read 8 byte from offset 0x64 diff --git a/tools/i2ctransfer.c b/tools/i2ctransfer.c index 4db98e3..446a174 100644 --- a/tools/i2ctransfer.c +++ b/tools/i2ctransfer.c @@ -52,9 +52,16 @@ static void help(void) " -V version info\n" " -y yes to all confirmations\n" " I2CBUS is an integer or an I2C bus name\n" - " DESC describes the transfer in the form: {r|w}LENGTH[@address]\n" - " 1) read/write-flag 2) LENGTH (range 0-65535, or '?')\n" - " 3) I2C address (use last one if omitted)\n" + " DESC describes the transfer in the form: [inpst]{r|w}LENGTH[@address]\n" + " 1) optional message modifier flags, if supported\n" + " i: ignore NACK from client\n" + " n: no master ACK/NACK bit in a read message\n" + " p: emit a STOP after the message\n" + " s: skip repeated start\n" + " t: toggle read/write bit\n" + " 2) mandatory read/write flag\n" + " 3) LENGTH (range 0-65535, or '?')\n" + " 4) I2C address (use last one if omitted)\n" " DATA are LENGTH bytes for a write message. They can be shortened by a suffix:\n" " = (keep value constant until LENGTH)\n" " + (increase value by 1 until LENGTH)\n" @@ -66,17 +73,20 @@ static void help(void) " # i2ctransfer 0 w17@0x50 0x42 0xff-\n"); } -static int check_funcs(int file) +static int get_funcs(int file, unsigned long *funcs) { - unsigned long funcs; - /* check adapter functionality */ - if (ioctl(file, I2C_FUNCS, &funcs) < 0) { + if (ioctl(file, I2C_FUNCS, funcs) < 0) { fprintf(stderr, "Error: Could not get the adapter " "functionality matrix: %s\n", strerror(errno)); return -1; } + return 0; +} + +static int check_funcs(unsigned long funcs) +{ if (!(funcs & I2C_FUNC_I2C)) { fprintf(stderr, MISSING_FUNC_FMT, "I2C transfers"); return -1; @@ -140,6 +150,85 @@ static int confirm(const char *filename, struct i2c_msg *msgs, __u32 nmsgs) return 1; } +/* + * Parse one message flag and check if the adapter supports it. + * Return: + * 1 if we have the direction of the message (read or write) + * 0 if the argument is a valid and supported optional flag + * -1 for unsupported flag + */ +static int add_flag_if_supported(__u16 *flags, unsigned long funcs, char arg) +{ + int mangling = 0, nostart = 0; + + /* Get the message flag from the argument */ + switch (arg) { + /* mandatory direction flag: ends the parsing of flags */ + case 'r': + *flags |= I2C_M_RD; + return 1; + case 'w': + return 1; + + /* optional flags */ +#ifdef I2C_M_IGNORE_NAK + case 'i': + *flags |= I2C_M_IGNORE_NAK; + mangling = 1; + break; +#endif +#ifdef I2C_M_NO_RD_ACK + case 'n': + *flags |= I2C_M_NO_RD_ACK; + mangling = 1; + break; +#endif +#ifdef I2C_M_STOP + case 'p': + *flags |= I2C_M_STOP; + mangling = 1; + break; +#endif +#ifdef I2C_M_NOSTART + case 's': + *flags |= I2C_M_NOSTART; + nostart = 1; + break; +#endif +#ifdef I2C_M_REV_DIR_ADDR + case 't': + *flags |= I2C_M_REV_DIR_ADDR; + mangling = 1; + break; +#endif + + default: + fprintf(stderr, "Error: Unsupported flag '%c'\n", arg); + return -1; + } + + /* Check that the adapter supports the requested flags */ +#ifdef I2C_FUNC_PROTOCOL_MANGLING + if (funcs & I2C_FUNC_PROTOCOL_MANGLING) + mangling = 0; +#endif + if (mangling) { + fprintf(stderr, MISSING_FUNC_FMT, "protocol mangling"); + return -1; + } + +#ifdef I2C_FUNC_NOSTART + if (funcs & I2C_FUNC_NOSTART) + nostart = 0; +#endif + if (nostart) { + fprintf(stderr, MISSING_FUNC_FMT, "repeated start skipping"); + return -1; + } + + return 0; +} + int main(int argc, char *argv[]) { char filename[20]; @@ -148,6 +237,7 @@ int main(int argc, char *argv[]) struct i2c_msg msgs[I2C_RDRW_IOCTL_MAX_MSGS]; enum parse_state state = PARSE_GET_DESC; unsigned int buf_idx = 0; + unsigned long funcs; memset(msgs, 0, sizeof(msgs)); @@ -182,7 +272,7 @@ int main(int argc, char *argv[]) exit(1); file = open_i2c_dev(i2cbus, filename, sizeof(filename), 0); - if (file < 0 || check_funcs(file)) + if (file < 0 || get_funcs(file, &funcs) || check_funcs(funcs)) exit(1); while (optind < argc) { @@ -191,6 +281,7 @@ int main(int argc, char *argv[]) __u16 flags; __u8 data, *buf; char *end; + int ret; if (nmsgs == I2C_RDRW_IOCTL_MAX_MSGS) { fprintf(stderr, "Error: Too many messages (max: %d)\n", @@ -202,11 +293,13 @@ int main(int argc, char *argv[]) case PARSE_GET_DESC: flags = 0; - switch (*arg_ptr++) { - case 'r': flags |= I2C_M_RD; break; - case 'w': break; - default: - fprintf(stderr, "Error: Invalid direction\n"); + for (ret = 0; *arg_ptr && !ret; arg_ptr++) { + ret = add_flag_if_supported(&flags, funcs, *arg_ptr); + if (ret < 0) + goto err_out_with_arg; + } + if (ret != 1) { + fprintf(stderr, "Error: Missing direction flag 'r' or 'w'\n"); goto err_out_with_arg; } -- 2.52.0