From: Bartosz Golaszewski <bgolaszewski@baylibre.com>
To: Wolfram Sang <wsa@the-dreams.de>
Cc: linux-i2c <linux-i2c@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
Bartosz Golaszewski <bgolaszewski@baylibre.com>
Subject: [RESEND PATCH v2 4/9] eeprom: at24: support reading of the serial number
Date: Wed, 2 Dec 2015 11:25:21 +0100 [thread overview]
Message-ID: <1449051926-21918-5-git-send-email-bgolaszewski@baylibre.com> (raw)
In-Reply-To: <1449051926-21918-1-git-send-email-bgolaszewski@baylibre.com>
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 <bgolaszewski@baylibre.com>
---
drivers/misc/eeprom/at24.c | 71 ++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 71 insertions(+)
diff --git a/drivers/misc/eeprom/at24.c b/drivers/misc/eeprom/at24.c
index 08cc327..6182f47 100644
--- a/drivers/misc/eeprom/at24.c
+++ b/drivers/misc/eeprom/at24.c
@@ -163,6 +163,77 @@ 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;
+
+ mutex_lock(&at24->lock);
+
+ 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) {
+ mutex_unlock(&at24->lock);
+ return count;
+ }
+
+ /* REVISIT: at HZ=100, this is sloooow */
+ msleep(1);
+ } while (time_before(read_time, timeout));
+
+ mutex_unlock(&at24->lock);
+
+ return -ETIMEDOUT;
+}
+
static ssize_t at24_eeprom_read(struct at24_data *at24, char *buf,
unsigned offset, size_t count)
{
--
2.1.4
next prev parent reply other threads:[~2015-12-02 10:27 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-12-02 10:25 [RESEND PATCH v2 0/9] eeprom: at24: at24cs series serial number read Bartosz Golaszewski
2015-12-02 10:25 ` [RESEND PATCH v2 1/9] eeprom: at24: platform_data: use BIT() macro Bartosz Golaszewski
2015-12-02 10:25 ` [RESEND PATCH v2 2/9] eeprom: at24: new flag in platform_data Bartosz Golaszewski
2015-12-02 10:25 ` [RESEND PATCH v2 3/9] eeprom: at24: tie up an additional address for at24cs series Bartosz Golaszewski
2015-12-02 10:25 ` Bartosz Golaszewski [this message]
2015-12-02 10:25 ` [RESEND PATCH v2 5/9] eeprom: at24: export the serial number through sysfs Bartosz Golaszewski
2015-12-02 10:25 ` [RESEND PATCH v2 6/9] eeprom: at24: improve the device_id table readability Bartosz Golaszewski
2015-12-02 10:25 ` [RESEND PATCH v2 7/9] eeprom: at24: add the at24cs series to the list of supported devices Bartosz Golaszewski
2015-12-02 10:25 ` [RESEND PATCH v2 8/9] eeprom: at24: remove a reduntant if Bartosz Golaszewski
2015-12-02 10:25 ` [RESEND PATCH v2 9/9] eeprom: at24: readability tweaks Bartosz Golaszewski
2015-12-11 12:08 ` [RESEND PATCH v2 0/9] eeprom: at24: at24cs series serial number read Wolfram Sang
2015-12-11 13:55 ` Bartosz Golaszewski
2015-12-21 14:29 ` Bartosz Golaszewski
2016-01-02 20:50 ` Wolfram Sang
2016-01-04 14:01 ` Bartosz Golaszewski
2016-01-05 18:58 ` Wolfram Sang
2016-01-07 16:10 ` Bartosz Golaszewski
2016-01-09 21:09 ` Wolfram Sang
2016-01-11 13:57 ` Bartosz Golaszewski
-- strict thread matches above, loose matches on Subject: below --
2015-11-24 9:44 Bartosz Golaszewski
2015-11-24 9:44 ` [RESEND PATCH v2 4/9] eeprom: at24: support reading of the serial number Bartosz Golaszewski
2015-11-17 9:52 [RESEND PATCH v2 0/9] eeprom: at24: at24cs series serial number read Bartosz Golaszewski
2015-11-17 9:52 ` [RESEND PATCH v2 4/9] eeprom: at24: support reading of the serial number Bartosz Golaszewski
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=1449051926-21918-5-git-send-email-bgolaszewski@baylibre.com \
--to=bgolaszewski@baylibre.com \
--cc=linux-i2c@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=wsa@the-dreams.de \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).