This patch adds an interface by which other kernel code can read/write
persistent memory such as i2c or SPI EEPROMs, or devices which provide
NVRAM. Use cases include storage of board-specific configuration data
like Ethernet addresses and sensor calibrations, as
As an example, the at24 EEPROM driver is updated to use this
interface.
In the case of at24 EEPROM, the platform code registers a 'setup'
callback with the at24_platform_data. When the at24 driver detects an
EEPROM, it fills out the read and write functions of the
memory_accessor and calls the setup callback passing the
memory_accessor struct. The platform code can then use the read/write
functions in the memory_accessor struct for reading and writing the
EEPROM.
Original idea, review and updates by David Brownell.
Cc: David Brownell <[email protected]>
Signed-off-by: Kevin Hilman <[email protected]>
---
Applies against v2.6.29-rc7.
Differences from v1: updated subject and added example use cases to
description.
drivers/misc/eeprom/at24.c | 42 +++++++++++++++++++++++++++++++++++-------
include/linux/i2c/at24.h | 4 ++++
include/linux/memory.h | 11 +++++++++++
3 files changed, 50 insertions(+), 7 deletions(-)
diff --git a/drivers/misc/eeprom/at24.c b/drivers/misc/eeprom/at24.c
index d477552..80bf7ab 100644
--- a/drivers/misc/eeprom/at24.c
+++ b/drivers/misc/eeprom/at24.c
@@ -53,6 +53,7 @@
struct at24_data {
struct at24_platform_data chip;
+ struct memory_accessor macc;
bool use_smbus;
/*
@@ -264,13 +265,6 @@ static ssize_t at24_bin_read(struct kobject *kobj, struct bin_attribute *attr,
/*
- * REVISIT: export at24_bin{read,write}() to let other kernel code use
- * eeprom data. For example, it might hold a board's Ethernet address, or
- * board-specific calibration data generated on the manufacturing floor.
- */
-
-
-/*
* Note that if the hardware write-protect pin is pulled high, the whole
* chip is normally write protected. But there are plenty of product
* variants here, including OTP fuses and partial chip protect.
@@ -386,6 +380,30 @@ static ssize_t at24_bin_write(struct kobject *kobj, struct bin_attribute *attr,
/*-------------------------------------------------------------------------*/
+/*
+ * This lets other kernel code access the eeprom data. For example, it
+ * might hold a board's Ethernet address, or board-specific calibration
+ * data generated on the manufacturing floor.
+ */
+
+static ssize_t at24_read(struct memory_accessor *macc, char *buf,
+ off_t offset, size_t count)
+{
+ struct at24_data *at24 = container_of(macc, struct at24_data, macc);
+
+ return at24_eeprom_read(at24, buf, offset, count);
+}
+
+static ssize_t at24_write(struct memory_accessor *macc, char *buf,
+ off_t offset, size_t count)
+{
+ struct at24_data *at24 = container_of(macc, struct at24_data, macc);
+
+ return at24_eeprom_write(at24, buf, offset, count);
+}
+
+/*-------------------------------------------------------------------------*/
+
static int at24_probe(struct i2c_client *client, const struct i2c_device_id *id)
{
struct at24_platform_data chip;
@@ -413,6 +431,9 @@ static int at24_probe(struct i2c_client *client, const struct i2c_device_id *id)
* is recommended anyhow.
*/
chip.page_size = 1;
+
+ chip.setup = NULL;
+ chip.context = NULL;
}
if (!is_power_of_2(chip.byte_len))
@@ -449,6 +470,9 @@ static int at24_probe(struct i2c_client *client, const struct i2c_device_id *id)
goto err_out;
}
+ at24->macc.read = at24_read;
+ at24->macc.write = at24_write;
+
mutex_init(&at24->lock);
at24->use_smbus = use_smbus;
at24->chip = chip;
@@ -520,6 +544,10 @@ static int at24_probe(struct i2c_client *client, const struct i2c_device_id *id)
at24->write_max,
use_smbus ? ", use_smbus" : "");
+ /* export data to kernel code */
+ if (chip.setup)
+ chip.setup(&at24->macc, chip.context);
+
return 0;
err_clients:
diff --git a/include/linux/i2c/at24.h b/include/linux/i2c/at24.h
index f6edd52..85b4f7e 100644
--- a/include/linux/i2c/at24.h
+++ b/include/linux/i2c/at24.h
@@ -2,6 +2,7 @@
#define _LINUX_AT24_H
#include <linux/types.h>
+#include <linux/memory.h>
/*
* As seen through Linux I2C, differences between the most common types of I2C
@@ -23,6 +24,9 @@ struct at24_platform_data {
#define AT24_FLAG_READONLY 0x40 /* sysfs-entry will be read-only */
#define AT24_FLAG_IRUGO 0x20 /* sysfs-entry will be world-readable */
#define AT24_FLAG_TAKE8ADDR 0x10 /* take always 8 addresses (24c00) */
+
+ int (*setup)(struct memory_accessor *, void *context);
+ void *context;
};
#endif /* _LINUX_AT24_H */
diff --git a/include/linux/memory.h b/include/linux/memory.h
index 3fdc108..aa97724 100644
--- a/include/linux/memory.h
+++ b/include/linux/memory.h
@@ -99,4 +99,15 @@ enum mem_add_context { BOOT, HOTPLUG };
#define hotplug_memory_notifier(fn, pri) do { } while (0)
#endif
+/*
+ * 'struct memory_accessor' is a generic interface to provide
+ * in-kernel access to persistent memory such as i2c or SPI EEPROMs
+ */
+struct memory_accessor {
+ ssize_t (*read)(struct memory_accessor *, char *buf, off_t offset,
+ size_t count);
+ ssize_t (*write)(struct memory_accessor *, char *buf, off_t offset,
+ size_t count);
+};
+
#endif /* _LINUX_MEMORY_H_ */
--
1.6.1.3
I was kind of hoping you'd address the locking and chunking
comments I made ... I'll ack if it includes something like
the appended patch.
---
drivers/misc/eeprom/at24.c | 43 ++++++++++++++++++++++++++++---------------
1 file changed, 28 insertions(+), 15 deletions(-)
--- a/drivers/misc/eeprom/at24.c
+++ b/drivers/misc/eeprom/at24.c
@@ -226,14 +226,11 @@ static ssize_t at24_eeprom_read(struct a
return status;
}
-static ssize_t at24_bin_read(struct kobject *kobj, struct bin_attribute *attr,
+static ssize_t at24_read(struct at24_data *at24,
char *buf, loff_t off, size_t count)
{
- struct at24_data *at24;
ssize_t retval = 0;
- at24 = dev_get_drvdata(container_of(kobj, struct device, kobj));
-
if (unlikely(!count))
return count;
@@ -263,6 +260,15 @@ static ssize_t at24_bin_read(struct kobj
return retval;
}
+static ssize_t at24_bin_read(struct kobject *kobj, struct bin_attribute *attr,
+ char *buf, loff_t off, size_t count)
+{
+ struct at24_data *at24;
+
+ at24 = dev_get_drvdata(container_of(kobj, struct device, kobj));
+ return at24_read(at24, buf, off, count);
+}
+
/*
* Note that if the hardware write-protect pin is pulled high, the whole
@@ -341,14 +347,11 @@ static ssize_t at24_eeprom_write(struct
return -ETIMEDOUT;
}
-static ssize_t at24_bin_write(struct kobject *kobj, struct bin_attribute *attr,
+static ssize_t at24_write(struct at24_data *at24,
char *buf, loff_t off, size_t count)
{
- struct at24_data *at24;
ssize_t retval = 0;
- at24 = dev_get_drvdata(container_of(kobj, struct device, kobj));
-
if (unlikely(!count))
return count;
@@ -378,6 +381,15 @@ static ssize_t at24_bin_write(struct kob
return retval;
}
+static ssize_t at24_bin_write(struct kobject *kobj, struct bin_attribute *attr,
+ char *buf, loff_t off, size_t count)
+{
+ struct at24_data *at24;
+
+ at24 = dev_get_drvdata(container_of(kobj, struct device, kobj));
+ return at24_write(at24, buf, off, count);
+}
+
/*-------------------------------------------------------------------------*/
/*
@@ -386,20 +398,20 @@ static ssize_t at24_bin_write(struct kob
* data generated on the manufacturing floor.
*/
-static ssize_t at24_read(struct memory_accessor *macc, char *buf,
+static ssize_t at24_macc_read(struct memory_accessor *macc, char *buf,
off_t offset, size_t count)
{
struct at24_data *at24 = container_of(macc, struct at24_data, macc);
- return at24_eeprom_read(at24, buf, offset, count);
+ return at24_read(at24, buf, offset, count);
}
-static ssize_t at24_write(struct memory_accessor *macc, char *buf,
+static ssize_t at24_macc_write(struct memory_accessor *macc, char *buf,
off_t offset, size_t count)
{
struct at24_data *at24 = container_of(macc, struct at24_data, macc);
- return at24_eeprom_write(at24, buf, offset, count);
+ return at24_write(at24, buf, offset, count);
}
/*-------------------------------------------------------------------------*/
@@ -470,9 +482,6 @@ static int at24_probe(struct i2c_client
goto err_out;
}
- at24->macc.read = at24_read;
- at24->macc.write = at24_write;
-
mutex_init(&at24->lock);
at24->use_smbus = use_smbus;
at24->chip = chip;
@@ -487,6 +496,8 @@ static int at24_probe(struct i2c_client
at24->bin.read = at24_bin_read;
at24->bin.size = chip.byte_len;
+ at24->macc.read = at24_macc_read;
+
writable = !(chip.flags & AT24_FLAG_READONLY);
if (writable) {
if (!use_smbus || i2c_check_functionality(client->adapter,
@@ -494,6 +505,8 @@ static int at24_probe(struct i2c_client
unsigned write_max = chip.page_size;
+ at24->macc.write = at24_macc_write;
+
at24->bin.write = at24_bin_write;
at24->bin.attr.mode |= S_IWUSR;
David Brownell <[email protected]> writes:
> I was kind of hoping you'd address the locking and chunking
> comments I made ... I'll ack if it includes something like
> the appended patch.
Sorry, somehow I missed those comments on the first round, I will
incorporate and resubmit.
Kevin
> ---
> drivers/misc/eeprom/at24.c | 43 ++++++++++++++++++++++++++++---------------
> 1 file changed, 28 insertions(+), 15 deletions(-)
>
> --- a/drivers/misc/eeprom/at24.c
> +++ b/drivers/misc/eeprom/at24.c
> @@ -226,14 +226,11 @@ static ssize_t at24_eeprom_read(struct a
> return status;
> }
>
> -static ssize_t at24_bin_read(struct kobject *kobj, struct bin_attribute *attr,
> +static ssize_t at24_read(struct at24_data *at24,
> char *buf, loff_t off, size_t count)
> {
> - struct at24_data *at24;
> ssize_t retval = 0;
>
> - at24 = dev_get_drvdata(container_of(kobj, struct device, kobj));
> -
> if (unlikely(!count))
> return count;
>
> @@ -263,6 +260,15 @@ static ssize_t at24_bin_read(struct kobj
> return retval;
> }
>
> +static ssize_t at24_bin_read(struct kobject *kobj, struct bin_attribute *attr,
> + char *buf, loff_t off, size_t count)
> +{
> + struct at24_data *at24;
> +
> + at24 = dev_get_drvdata(container_of(kobj, struct device, kobj));
> + return at24_read(at24, buf, off, count);
> +}
> +
>
> /*
> * Note that if the hardware write-protect pin is pulled high, the whole
> @@ -341,14 +347,11 @@ static ssize_t at24_eeprom_write(struct
> return -ETIMEDOUT;
> }
>
> -static ssize_t at24_bin_write(struct kobject *kobj, struct bin_attribute *attr,
> +static ssize_t at24_write(struct at24_data *at24,
> char *buf, loff_t off, size_t count)
> {
> - struct at24_data *at24;
> ssize_t retval = 0;
>
> - at24 = dev_get_drvdata(container_of(kobj, struct device, kobj));
> -
> if (unlikely(!count))
> return count;
>
> @@ -378,6 +381,15 @@ static ssize_t at24_bin_write(struct kob
> return retval;
> }
>
> +static ssize_t at24_bin_write(struct kobject *kobj, struct bin_attribute *attr,
> + char *buf, loff_t off, size_t count)
> +{
> + struct at24_data *at24;
> +
> + at24 = dev_get_drvdata(container_of(kobj, struct device, kobj));
> + return at24_write(at24, buf, off, count);
> +}
> +
> /*-------------------------------------------------------------------------*/
>
> /*
> @@ -386,20 +398,20 @@ static ssize_t at24_bin_write(struct kob
> * data generated on the manufacturing floor.
> */
>
> -static ssize_t at24_read(struct memory_accessor *macc, char *buf,
> +static ssize_t at24_macc_read(struct memory_accessor *macc, char *buf,
> off_t offset, size_t count)
> {
> struct at24_data *at24 = container_of(macc, struct at24_data, macc);
>
> - return at24_eeprom_read(at24, buf, offset, count);
> + return at24_read(at24, buf, offset, count);
> }
>
> -static ssize_t at24_write(struct memory_accessor *macc, char *buf,
> +static ssize_t at24_macc_write(struct memory_accessor *macc, char *buf,
> off_t offset, size_t count)
> {
> struct at24_data *at24 = container_of(macc, struct at24_data, macc);
>
> - return at24_eeprom_write(at24, buf, offset, count);
> + return at24_write(at24, buf, offset, count);
> }
>
> /*-------------------------------------------------------------------------*/
> @@ -470,9 +482,6 @@ static int at24_probe(struct i2c_client
> goto err_out;
> }
>
> - at24->macc.read = at24_read;
> - at24->macc.write = at24_write;
> -
> mutex_init(&at24->lock);
> at24->use_smbus = use_smbus;
> at24->chip = chip;
> @@ -487,6 +496,8 @@ static int at24_probe(struct i2c_client
> at24->bin.read = at24_bin_read;
> at24->bin.size = chip.byte_len;
>
> + at24->macc.read = at24_macc_read;
> +
> writable = !(chip.flags & AT24_FLAG_READONLY);
> if (writable) {
> if (!use_smbus || i2c_check_functionality(client->adapter,
> @@ -494,6 +505,8 @@ static int at24_probe(struct i2c_client
>
> unsigned write_max = chip.page_size;
>
> + at24->macc.write = at24_macc_write;
> +
> at24->bin.write = at24_bin_write;
> at24->bin.attr.mode |= S_IWUSR;
>