From patchwork Mon Oct 12 14:31:16 2015 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Bartosz Golaszewski X-Patchwork-Id: 529131 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id 5D2C9140134 for ; Tue, 13 Oct 2015 01:36:06 +1100 (AEDT) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752682AbbJLOcG (ORCPT ); Mon, 12 Oct 2015 10:32:06 -0400 Received: from mail-wi0-f182.google.com ([209.85.212.182]:37739 "EHLO mail-wi0-f182.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752266AbbJLOcE (ORCPT ); Mon, 12 Oct 2015 10:32:04 -0400 Received: by wijq8 with SMTP id q8so60827309wij.0 for ; Mon, 12 Oct 2015 07:32:03 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references; bh=TXF4Keb3V51+tunLQw1z82G4BpXoehtJ+9x/8crWX2Q=; b=a0qisYWRzhPU46HRxOysEaGqFMyOg9izlQ01HrOLToYoCXlxk5tLHjioaRnagxH81Y krYULQTCgTOrFPv4mmtKsl2sXYDT+vqDENnv1K00+xtyCG7Twwu3vYSr2dnvIFbTF7QM VDvWn9w58Kq1tkoS006ycfpHkqMyuuPtQpp4CH1CApAOxJdwqqs2UMzi2V3OMvZrvylZ BGdle56YkG1b6fjJBD9txhWo2/wM5tngMd+fjaD6x2Sq30as66b+5/rZvh0QyoElyZFU i9LgFPZp5Hut4X5beOC6BL3ZpxAeKfJlGNc7bUdADFV+vhgV2jN64biTjAt4Sh0CbjUJ xfHQ== X-Gm-Message-State: ALoCoQm3DJMmwBrFPyyPb3ZjmHNrcY/XSSPtchA2Z5K23beqGRqEhWDTJYk6syP+FlJsGLgRxzgM X-Received: by 10.180.8.68 with SMTP id p4mr15261196wia.16.1444660323771; Mon, 12 Oct 2015 07:32:03 -0700 (PDT) Received: from localhost.localdomain (LPoitiers-656-1-62-228.w90-63.abo.wanadoo.fr. [90.63.143.228]) by smtp.gmail.com with ESMTPSA id az6sm11102907wib.12.2015.10.12.07.31.59 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Mon, 12 Oct 2015 07:32:03 -0700 (PDT) From: Bartosz Golaszewski To: Wolfram Sang Cc: linux-i2c , LKML , Patrick Titiano , Bartosz Golaszewski Subject: [PATCH 4/9] eeprom: at24: support reading of the serial number Date: Mon, 12 Oct 2015 16:31:16 +0200 Message-Id: <1444660281-19150-5-git-send-email-bgolaszewski@baylibre.com> X-Mailer: git-send-email 2.1.4 In-Reply-To: <1444660281-19150-1-git-send-email-bgolaszewski@baylibre.com> References: <1444660281-19150-1-git-send-email-bgolaszewski@baylibre.com> Sender: linux-i2c-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-i2c@vger.kernel.org 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 | 65 ++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 65 insertions(+) diff --git a/drivers/misc/eeprom/at24.c b/drivers/misc/eeprom/at24.c index 3a75a52..4d4a793 100644 --- a/drivers/misc/eeprom/at24.c +++ b/drivers/misc/eeprom/at24.c @@ -156,6 +156,71 @@ static struct i2c_client *at24_translate_offset(struct at24_data *at24, return at24->client[i]; } +static int __attribute__((unused)) at24cs_eeprom_serial_read( + struct at24_data *at24, + char *buf, unsigned offset, + size_t count) +{ + unsigned long timeout, read_time; + struct i2c_client *client; + struct i2c_msg msg[2]; + u8 addrbuf[2]; + int status; + + client = at24->client[1]; + + 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; + + /* + * Reads fail if the previous write didn't complete yet. We may + * loop a few times until this one succeeds, waiting at least + * long enough for one entire page write to work. + */ + timeout = jiffies + msecs_to_jiffies(write_timeout); + do { + read_time = jiffies; + status = i2c_transfer(client->adapter, msg, 2); + if (status == 2) + return count; + + /* REVISIT: at HZ=100, this is sloooow */ + msleep(1); + } 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) {