Some inline comments below.
Regards
Matthias
Am 22.02.23 um 14:29 schrieb Tomi Valkeinen:
From: Luca Ceresoli <luca@xxxxxxxxxxxxxxxx>
An ATR is a device that looks similar to an i2c-mux: it has an I2C
slave "upstream" port and N master "downstream" ports, and forwards
transactions from upstream to the appropriate downstream port. But it
is different in that the forwarded transaction has a different slave
address. The address used on the upstream bus is called the "alias"
and is (potentially) different from the physical slave address of the
downstream chip.
Add a helper file (just like i2c-mux.c for a mux or switch) to allow
implementing ATR features in a device driver. The helper takes care or
adapter creation/destruction and translates addresses at each transaction.
Signed-off-by: Luca Ceresoli <luca@xxxxxxxxxxxxxxxx>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@xxxxxxxxxxxxxxxx>
---
Documentation/i2c/index.rst | 1 +
Documentation/i2c/muxes/i2c-atr.rst | 97 +++++
MAINTAINERS | 8 +
drivers/i2c/Kconfig | 9 +
drivers/i2c/Makefile | 1 +
drivers/i2c/i2c-atr.c | 548 ++++++++++++++++++++++++++++
include/linux/i2c-atr.h | 116 ++++++
7 files changed, 780 insertions(+)
create mode 100644 Documentation/i2c/muxes/i2c-atr.rst
create mode 100644 drivers/i2c/i2c-atr.c
create mode 100644 include/linux/i2c-atr.h
[...]
diff --git a/drivers/i2c/i2c-atr.c b/drivers/i2c/i2c-atr.c
new file mode 100644
index 000000000000..5ab890b83670
--- /dev/null
+++ b/drivers/i2c/i2c-atr.c
@@ -0,0 +1,548 @@
[...]
+
+/*
+ * Replace all message addresses with their aliases, saving the original
+ * addresses.
+ *
+ * This function is internal for use in i2c_atr_master_xfer(). It must be
+ * followed by i2c_atr_unmap_msgs() to restore the original addresses.
+ */
+static int i2c_atr_map_msgs(struct i2c_atr_chan *chan, struct i2c_msg *msgs,
+ int num)
+{
+ struct i2c_atr *atr = chan->atr;
+ static struct i2c_atr_cli2alias_pair *c2a;
+ int i;
+
+ /* Ensure we have enough room to save the original addresses */
+ if (unlikely(chan->orig_addrs_size < num)) {
+ u16 *new_buf;
+
+ /* We don't care about old data, hence no realloc() */
+ new_buf = kmalloc_array(num, sizeof(*new_buf), GFP_KERNEL);
+ if (!new_buf)
+ return -ENOMEM;
+
+ kfree(chan->orig_addrs);
+ chan->orig_addrs = new_buf;
+ chan->orig_addrs_size = num;
+ }
+
+ for (i = 0; i < num; i++) {
+ chan->orig_addrs[i] = msgs[i].addr;
+
+ c2a = i2c_atr_find_mapping_by_addr(&chan->alias_list,
+ msgs[i].addr);
+ if (!c2a) {
+ dev_err(atr->dev, "client 0x%02x not mapped!\n",
+ msgs[i].addr);
+ return -ENXIO;
I miss the roll-back of previously modified msgs[].addr values.
+ }
+
+ msgs[i].addr = c2a->alias;
+ }
+
+ return 0;
+}
+
+/*
+ * Restore all message address aliases with the original addresses. This
+ * function is internal for use in i2c_atr_master_xfer().
+ *
+ * @see i2c_atr_map_msgs()
+ */
+static void i2c_atr_unmap_msgs(struct i2c_atr_chan *chan, struct i2c_msg *msgs,
+ int num)
+{
+ int i;
+
+ for (i = 0; i < num; i++)
+ msgs[i].addr = chan->orig_addrs[i];
Does this code needs null and size checks for orig_addrs/orig_addrs_size
to protect from oopses?
This cannot happen now as i2c_atr_master_xfer returns early when
i2c_atr_map_msgs fails.
+}
+
+static int i2c_atr_master_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
+ int num)
+{
+ struct i2c_atr_chan *chan = adap->algo_data;
+ struct i2c_atr *atr = chan->atr;
+ struct i2c_adapter *parent = atr->parent;
+ int ret;
+
+ /* Translate addresses */
+ mutex_lock(&chan->orig_addrs_lock);
+
+ ret = i2c_atr_map_msgs(chan, msgs, num);
+ if (ret < 0)
+ goto err_unlock;
+
+ /* Perform the transfer */
+ ret = i2c_transfer(parent, msgs, num);
+
+ /* Restore addresses */
+ i2c_atr_unmap_msgs(chan, msgs, num);
+
+err_unlock:
+ mutex_unlock(&chan->orig_addrs_lock);
+
+ return ret;
+}
+
[...]
