Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752104AbcCXOxq (ORCPT ); Thu, 24 Mar 2016 10:53:46 -0400 Received: from mail-wm0-f42.google.com ([74.125.82.42]:36869 "EHLO mail-wm0-f42.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752400AbcCXOqU (ORCPT ); Thu, 24 Mar 2016 10:46:20 -0400 From: Bartosz Golaszewski To: Wolfram Sang , linux-i2c , LKML Cc: Andrew Lunn , Bartosz Golaszewski Subject: [PATCH 07/13] eeprom: at24: support reading of the serial number Date: Thu, 24 Mar 2016 15:46:01 +0100 Message-Id: <1458830767-23816-8-git-send-email-bgolaszewski@baylibre.com> X-Mailer: git-send-email 2.1.4 In-Reply-To: <1458830767-23816-1-git-send-email-bgolaszewski@baylibre.com> References: <1458830767-23816-1-git-send-email-bgolaszewski@baylibre.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2395 Lines: 84 The at24cs series EEPROM chips have an additional read-only memory area containing a factory pre-programmed serial number. In order to access it, one has to perform a dummy write before reading the serial number bytes. Add a function that allows to access the serial number. Signed-off-by: Bartosz Golaszewski --- drivers/misc/eeprom/at24.c | 59 ++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 59 insertions(+) diff --git a/drivers/misc/eeprom/at24.c b/drivers/misc/eeprom/at24.c index bc5be1e..a7d6c15 100644 --- a/drivers/misc/eeprom/at24.c +++ b/drivers/misc/eeprom/at24.c @@ -159,6 +159,65 @@ static struct i2c_client *at24_translate_offset(struct at24_data *at24, return at24->client[i]; } +static int __attribute__((unused)) +at24cs_serial_read(struct at24_data *at24, + char *buf, loff_t off, size_t count) +{ + unsigned long timeout, read_time; + struct i2c_client *client; + unsigned int offset = off; + struct i2c_msg msg[2]; + u8 addrbuf[2]; + int status; + + client = at24_translate_offset(at24, &offset); + + memset(msg, 0, sizeof(msg)); + msg[0].addr = client->addr; + msg[0].buf = addrbuf; + + /* + * The address pointer of the device is shared between the regular + * EEPROM array and the serial number block. The dummy write (part of + * the sequential read protocol) ensures the address pointer is reset + * to the desired position. + */ + if (at24->chip.flags & AT24_FLAG_ADDR16) { + /* + * For 16 bit address pointers, the word address must contain + * a '10' sequence in bits 11 and 10 regardless of the + * intended position of the address pointer. + */ + addrbuf[0] = 0x08; + addrbuf[1] = offset; + msg[0].len = 2; + } else { + /* + * Otherwise the word address must begin with a '10' sequence, + * regardless of the intended address. + */ + addrbuf[0] = 0x80 + offset; + msg[0].len = 1; + } + + msg[1].addr = client->addr; + msg[1].flags = I2C_M_RD; + msg[1].buf = buf; + msg[1].len = count; + + timeout = jiffies + msecs_to_jiffies(write_timeout); + do { + read_time = jiffies; + status = i2c_transfer(client->adapter, msg, 2); + if (status == 2) + return count; + + usleep_range(1000, 1500); + } while (time_before(read_time, timeout)); + + return -ETIMEDOUT; +} + static ssize_t at24_eeprom_read(struct at24_data *at24, char *buf, unsigned offset, size_t count) { -- 2.7.4