Re: [PATCH 3/3] i2c: mux: pca9541: prepare for PCA9641 support

[Guenter Roeck]

On 03/20/2018 04:17 PM, Vladimir Zapolskiy wrote:

Hi Peter, Ken,

On 03/20/2018 11:32 AM, Peter Rosin wrote:

Make the arbitrate and release_bus implementation chip specific.

by chance I took a look at the original implementation done by Ken, and
I would say that this 3/3 change is an overkill as a too generic one.
Is there any next observable extension? And do two abstracted (*arbitrate)
and (*release_bus) cover it well? Probably no.

At first it would be simpler to add a new chip id field into struct pca9541
(struct rename would be needed of course), and do a selection of specific
pca9x41_arbitrate() and pca9x41_release_bus() depending on it:

FWIW, I very much prefer Peter's code. I think it is much cleaner.

Guenter

----8<----
diff --git a/drivers/i2c/muxes/i2c-mux-pca9541.c 
b/drivers/i2c/muxes/i2c-mux-pca9541.c
index 47685eb..a40e6d8 100644
--- a/drivers/i2c/muxes/i2c-mux-pca9541.c
+++ b/drivers/i2c/muxes/i2c-mux-pca9541.c
@@ -70,8 +70,13 @@
  #define SELECT_DELAY_SHORT    50
  #define SELECT_DELAY_LONG     1000

+enum chip_id {

+       pca9541,
+};
+
  struct pca9541 {
        struct i2c_client *client;
+       enum chip_id id;
        unsigned long select_timeout;
        unsigned long arb_timeout;
  };
@@ -188,10 +193,13 @@ static int pca9541_reg_read(struct i2c_client *client, u8 
command)
   */

/* Release bus. Also reset NTESTON and BUSINIT if it was set. */

-static void pca9541_release_bus(struct i2c_client *client)
+static void pca9541_release_bus(struct i2c_client *client, enum chip_id id)
  {
        int reg;

+ if (id != pca9541)

+               return;
+
        reg = pca9541_reg_read(client, PCA9541_CONTROL);
        if (reg >= 0 && !pca9541_busoff(reg) && pca9541_mybus(reg))
                pca9541_reg_write(client, PCA9541_CONTROL,
@@ -235,12 +243,15 @@ static const u8 pca9541_control[16] = {
   *  0 : bus not acquired
   *  1 : bus acquired
   */
-static int pca9541_arbitrate(struct i2c_client *client)
+static int pca9541_arbitrate(struct i2c_client *client, enum chip_id id)
  {
        struct i2c_mux_core *muxc = i2c_get_clientdata(client);
        struct pca9541 *data = i2c_mux_priv(muxc);
        int reg;

+ if (id != pca9541)

+               return -EOPNOTSUPP;
+
        reg = pca9541_reg_read(client, PCA9541_CONTROL);
        if (reg < 0)
                return reg;
@@ -318,7 +329,7 @@ static int pca9541_select_chan(struct i2c_mux_core *muxc, 
u32 chan)
                /* force bus ownership after this time */

do {

-               ret = pca9541_arbitrate(client);
+               ret = pca9541_arbitrate(client, data->id);
                if (ret)
                        return ret < 0 ? ret : 0;

@@ -336,7 +347,7 @@ static int pca9541_release_chan(struct i2c_mux_core *muxc, u32 chan)

        struct pca9541 *data = i2c_mux_priv(muxc);
        struct i2c_client *client = data->client;

- pca9541_release_bus(client);

+       pca9541_release_bus(client, data->id);
        return 0;
  }

@@ -361,7 +372,7 @@ static int pca9541_probe(struct i2c_client *client,

         * We have to lock the adapter before releasing the bus.
         */
        i2c_lock_adapter(adap);
-       pca9541_release_bus(client);
+       pca9541_release_bus(client, pca9541);
        i2c_unlock_adapter(adap);

/* Create mux adapter */

@@ -377,6 +388,7 @@ static int pca9541_probe(struct i2c_client *client,

data = i2c_mux_priv(muxc);

        data->client = client;
+       data->id = pca9541;

i2c_set_clientdata(client, muxc); ----8<----

Signed-off-by: Peter Rosin <p...@axentia.se>
---
  drivers/i2c/muxes/i2c-mux-pca9541.c | 62 +++++++++++++++++++++++++++----------
  1 file changed, 45 insertions(+), 17 deletions(-)

The change above is trivial and it does not cancel any further
extensions similar to your idea, the open question is if there
is a demand right at the moment.

diff --git a/drivers/i2c/muxes/i2c-mux-pca9541.c 
b/drivers/i2c/muxes/i2c-mux-pca9541.c
index 47685eb4e0e9..cac629e36bf8 100644
--- a/drivers/i2c/muxes/i2c-mux-pca9541.c
+++ b/drivers/i2c/muxes/i2c-mux-pca9541.c
@@ -23,6 +23,7 @@
  #include <linux/i2c-mux.h>
  #include <linux/jiffies.h>
  #include <linux/module.h>
+#include <linux/of_device.h>
  #include <linux/platform_data/pca954x.h>
  #include <linux/slab.h>

@@ -70,26 +71,22 @@

  #define SELECT_DELAY_SHORT    50
  #define SELECT_DELAY_LONG     1000

-struct pca9541 {

-       struct i2c_client *client;
-       unsigned long select_timeout;
-       unsigned long arb_timeout;
+enum chip_name {

chip_name sound like a string storage, chip_id might be better here.

+       pca9541,
  };

--
With best wishes,
Vladimir