[PATCH v3 1/4] eeprom: ee1004: Enable devices on multiple busses

Eddie James
2023-03-22T14:04:25Z

The driver previously prevented probing devices on more than one
bus due to locking constraints with the special page addresses. This
constraint can be removed by allocating a reference-counted bus
structure containing the lock, rather than using global variables.

Signed-off-by: Eddie James <eajames@linux.ibm.com>
---
Changes since v2:
- Remove of_device.h include

drivers/misc/eeprom/ee1004.c | 174 +++++++++++++++++++++--------------
1 file changed, 105 insertions(+), 69 deletions(-)

diff --git a/drivers/misc/eeprom/ee1004.c b/drivers/misc/eeprom/ee1004.c
index c8c6deb7ed89..0aed5760e370 100644
--- a/drivers/misc/eeprom/ee1004.c
+++ b/drivers/misc/eeprom/ee1004.c
@@ -9,9 +9,11 @@
* Copyright (C) 2008 Wolfram Sang, Pengutronix
*/

+#include <linux/err.h>
#include <linux/i2c.h>
#include <linux/init.h>
#include <linux/kernel.h>
+#include <linux/list.h>
#include <linux/mod_devicetable.h>
#include <linux/module.h>
#include <linux/mutex.h>
@@ -31,20 +33,24 @@
* over performance.
*/

-#define EE1004_ADDR_SET_PAGE 0x36
+#define EE1004_ADDR_SET_PAGE0 0x36
+#define EE1004_ADDR_SET_PAGE1 0x37
#define EE1004_NUM_PAGES 2
#define EE1004_PAGE_SIZE 256
#define EE1004_PAGE_SHIFT 8
#define EE1004_EEPROM_SIZE (EE1004_PAGE_SIZE * EE1004_NUM_PAGES)

-/*
- * Mutex protects ee1004_set_page and ee1004_dev_count, and must be held
- * from page selection to end of read.
- */
-static DEFINE_MUTEX(ee1004_bus_lock);
-static struct i2c_client *ee1004_set_page[EE1004_NUM_PAGES];
-static unsigned int ee1004_dev_count;
-static int ee1004_current_page;
+struct ee1004_bus {
+ struct kref kref;
+ struct list_head list;
+ struct mutex lock;
+ struct i2c_adapter *adapter;
+ struct i2c_client *set_page_clients[EE1004_NUM_PAGES];
+ int page;
+};
+
+static LIST_HEAD(ee1004_busses);
+static DEFINE_MUTEX(ee1004_busses_lock);

static const struct i2c_device_id ee1004_ids[] = {
{ "ee1004", 0 },
@@ -54,11 +60,11 @@ MODULE_DEVICE_TABLE(i2c, ee1004_ids);

/*-------------------------------------------------------------------------*/

-static int ee1004_get_current_page(void)
+static int ee1004_get_current_page(struct ee1004_bus *bus)
{
int err;

- err = i2c_smbus_read_byte(ee1004_set_page[0]);
+ err = i2c_smbus_read_byte(bus->set_page_clients[0]);
if (err == -ENXIO) {
/* Nack means page 1 is selected */
return 1;
@@ -72,33 +78,30 @@ static int ee1004_get_current_page(void)
return 0;
}

-static int ee1004_set_current_page(struct device *dev, int page)
+static int ee1004_set_current_page(struct ee1004_bus *bus, int page)
{
int ret;

- if (page == ee1004_current_page)
+ if (page == bus->page)
return 0;

/* Data is ignored */
- ret = i2c_smbus_write_byte(ee1004_set_page[page], 0x00);
+ ret = i2c_smbus_write_byte(bus->set_page_clients[page], 0x00);
+
/*
* Don't give up just yet. Some memory modules will select the page
* but not ack the command. Check which page is selected now.
*/
- if (ret == -ENXIO && ee1004_get_current_page() == page)
+ if (ret == -ENXIO && ee1004_get_current_page(bus) == page)
ret = 0;
- if (ret < 0) {
- dev_err(dev, "Failed to select page %d (%d)\n", page, ret);
+ if (ret < 0)
return ret;
- }
-
- dev_dbg(dev, "Selected page %d\n", page);
- ee1004_current_page = page;

+ bus->page = page;
return 0;
}

-static ssize_t ee1004_eeprom_read(struct i2c_client *client, char *buf,
+static ssize_t ee1004_eeprom_read(struct i2c_client *client, struct ee1004_bus *bus, char *buf,
unsigned int offset, size_t count)
{
int status, page;
@@ -106,9 +109,11 @@ static ssize_t ee1004_eeprom_read(struct i2c_client *client, char *buf,
page = offset >> EE1004_PAGE_SHIFT;
offset &= (1 << EE1004_PAGE_SHIFT) - 1;

- status = ee1004_set_current_page(&client->dev, page);
- if (status)
+ status = ee1004_set_current_page(bus, page);
+ if (status) {
+ dev_err(&client->dev, "Failed to select page %d (%d)\n", page, status);
return status;
+ }

/* Can't cross page boundaries */
if (offset + count > EE1004_PAGE_SIZE)
@@ -125,6 +130,7 @@ static ssize_t eeprom_read(struct file *filp, struct kobject *kobj,
char *buf, loff_t off, size_t count)
{
struct i2c_client *client = kobj_to_i2c_client(kobj);
+ struct ee1004_bus *bus = i2c_get_clientdata(client);
size_t requested = count;
int ret = 0;

@@ -132,10 +138,10 @@ static ssize_t eeprom_read(struct file *filp, struct kobject *kobj,
* Read data from chip, protecting against concurrent access to
* other EE1004 SPD EEPROMs on the same adapter.
*/
- mutex_lock(&ee1004_bus_lock);
+ mutex_lock(&bus->lock);

while (count) {
- ret = ee1004_eeprom_read(client, buf, off, count);
+ ret = ee1004_eeprom_read(client, bus, buf, off, count);
if (ret < 0)
goto out;

@@ -144,7 +150,7 @@ static ssize_t eeprom_read(struct file *filp, struct kobject *kobj,
count -= ret;
}
out:
- mutex_unlock(&ee1004_bus_lock);
+ mutex_unlock(&bus->lock);

return ret < 0 ? ret : requested;
}
@@ -158,18 +164,56 @@ static struct bin_attribute *ee1004_attrs[] = {

BIN_ATTRIBUTE_GROUPS(ee1004);

-static void ee1004_cleanup(int idx)
+static void ee1004_bus_unregister(struct ee1004_bus *bus)
{
- if (--ee1004_dev_count == 0)
- while (--idx >= 0) {
- i2c_unregister_device(ee1004_set_page[idx]);
- ee1004_set_page[idx] = NULL;
- }
+ i2c_unregister_device(bus->set_page_clients[1]);
+ i2c_unregister_device(bus->set_page_clients[0]);
+}
+
+static void ee1004_bus_release(struct kref *kref)
+{
+ struct ee1004_bus *bus = container_of(kref, struct ee1004_bus, kref);
+
+ ee1004_bus_unregister(bus);
+
+ mutex_lock(&ee1004_busses_lock);
+ list_del(&bus->list);
+ mutex_unlock(&ee1004_busses_lock);
+
+ kfree(bus);
+}
+
+static int ee1004_bus_initialize(struct ee1004_bus *bus, struct i2c_adapter *adapter)
+{
+ bus->set_page_clients[0] = i2c_new_dummy_device(adapter, EE1004_ADDR_SET_PAGE0);
+ if (IS_ERR(bus->set_page_clients[0]))
+ return PTR_ERR(bus->set_page_clients[0]);
+
+ bus->set_page_clients[1] = i2c_new_dummy_device(adapter, EE1004_ADDR_SET_PAGE1);
+ if (IS_ERR(bus->set_page_clients[1])) {
+ i2c_unregister_device(bus->set_page_clients[0]);
+ return PTR_ERR(bus->set_page_clients[1]);
+ }
+
+ bus->page = ee1004_get_current_page(bus);
+ if (bus->page < 0) {
+ ee1004_bus_unregister(bus);
+ return bus->page;
+ }
+
+ kref_init(&bus->kref);
+ list_add(&bus->list, &ee1004_busses);
+ mutex_init(&bus->lock);
+ bus->adapter = adapter;
+
+ return 0;
}

static int ee1004_probe(struct i2c_client *client)
{
- int err, cnr = 0;
+ struct ee1004_bus *bus;
+ bool found = false;
+ int rc = 0;

/* Make sure we can operate on this adapter */
if (!i2c_check_functionality(client->adapter,
@@ -178,53 +222,45 @@ static int ee1004_probe(struct i2c_client *client)
I2C_FUNC_SMBUS_BYTE | I2C_FUNC_SMBUS_READ_BYTE_DATA))
return -EPFNOSUPPORT;

- /* Use 2 dummy devices for page select command */
- mutex_lock(&ee1004_bus_lock);
- if (++ee1004_dev_count == 1) {
- for (cnr = 0; cnr < EE1004_NUM_PAGES; cnr++) {
- struct i2c_client *cl;
-
- cl = i2c_new_dummy_device(client->adapter, EE1004_ADDR_SET_PAGE + cnr);
- if (IS_ERR(cl)) {
- err = PTR_ERR(cl);
- goto err_clients;
- }
- ee1004_set_page[cnr] = cl;
+ mutex_lock(&ee1004_busses_lock);
+ list_for_each_entry(bus, &ee1004_busses, list) {
+ if (bus->adapter == client->adapter) {
+ kref_get(&bus->kref);
+ found = true;
+ break;
+ }
+ }
+
+ if (!found) {
+ bus = kzalloc(sizeof(*bus), GFP_KERNEL);
+ if (!bus) {
+ rc = -ENOMEM;
+ goto unlock;
}

- /* Remember current page to avoid unneeded page select */
- err = ee1004_get_current_page();
- if (err < 0)
- goto err_clients;
- dev_dbg(&client->dev, "Currently selected page: %d\n", err);
- ee1004_current_page = err;
- } else if (client->adapter != ee1004_set_page[0]->adapter) {
- dev_err(&client->dev,
- "Driver only supports devices on a single I2C bus\n");
- err = -EOPNOTSUPP;
- goto err_clients;
+ rc = ee1004_bus_initialize(bus, client->adapter);
+ if (rc) {
+ kfree(bus);
+ goto unlock;
+ }
}
- mutex_unlock(&ee1004_bus_lock);
+
+ i2c_set_clientdata(client, bus);

dev_info(&client->dev,
"%u byte EE1004-compliant SPD EEPROM, read-only\n",
EE1004_EEPROM_SIZE);

- return 0;
-
- err_clients:
- ee1004_cleanup(cnr);
- mutex_unlock(&ee1004_bus_lock);
-
- return err;
+unlock:
+ mutex_unlock(&ee1004_busses_lock);
+ return rc;
}

static void ee1004_remove(struct i2c_client *client)
{
- /* Remove page select clients if this is the last device */
- mutex_lock(&ee1004_bus_lock);
- ee1004_cleanup(EE1004_NUM_PAGES);
- mutex_unlock(&ee1004_bus_lock);
+ struct ee1004_bus *bus = i2c_get_clientdata(client);
+
+ kref_put(&bus->kref, ee1004_bus_release);
}

/*-------------------------------------------------------------------------*/
--
2.31.1