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SubjectRe: [PATCH 3/3] i2c: mux: pca9541: prepare for PCA9641 support
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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 <peda@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
>

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