On Wed, Mar 10, 2010 at 4:44 AM, Jean Delvare <khali@xxxxxxxxxxxx> wrote:
> Hi Alex,
>
> Sorry for the late answer.
>
> On Mon, 11 Jan 2010 17:13:50 -0500, Alex Deucher wrote:
>> Hi,
>>
>> I'm adding support for the i2c controllers on radeon hardware and
>> I have a few questions. I have a radeon-algo that encapsulates all
>> the various hw i2c controller functionality, however, it uses a
>> bit-algo bus internally for cases where you have to use bit-banging
>> rather than the hardware i2c engines. Also, for bit banging to work
>> properly, you need to do some things before the bit-algo transaction
>> (basically masking the gpios for software use).
>
> There used to be a patch floating around that added pre- and post-xfer
> hooks to i2c-algo-bit... I couldn't find it again, so I rewrote it:
>
> From: Jean Delvare <khali@xxxxxxxxxxxx>
> Subject: i2c-algo-bit: Add pre- and post-xfer hooks
>
> Drivers might have to do random things before and/or after I2C
> transfers. Add hooks to the i2c-algo-bit implementation to let them do
> so.
>
> Signed-off-by: Jean Delvare <khali@xxxxxxxxxxxx>
> ---
> drivers/i2c/algos/i2c-algo-bit.c | 9 +++++++++
> include/linux/i2c-algo-bit.h | 2 ++
> 2 files changed, 11 insertions(+)
>
> --- linux-2.6.34-rc1.orig/drivers/i2c/algos/i2c-algo-bit.c 2009-06-10 05:05:27.000000000 +0200
> +++ linux-2.6.34-rc1/drivers/i2c/algos/i2c-algo-bit.c 2010-03-09 18:52:50.000000000 +0100
> @@ -522,6 +522,12 @@ static int bit_xfer(struct i2c_adapter *
> int i, ret;
> unsigned short nak_ok;
>
> + if (adap->pre_xfer) {
> + ret = adap->pre_xfer(i2c_adap, adap->data);
> + if (ret < 0)
> + return ret;
> + }
> +
> bit_dbg(3, &i2c_adap->dev, "emitting start condition\n");
> i2c_start(adap);
> for (i = 0; i < num; i++) {
> @@ -570,6 +576,9 @@ static int bit_xfer(struct i2c_adapter *
> bailout:
> bit_dbg(3, &i2c_adap->dev, "emitting stop condition\n");
> i2c_stop(adap);
> +
> + if (adap->post_xfer)
> + adap->post_xfer(i2c_adap, adap->data);
> return ret;
> }
>
> --- linux-2.6.34-rc1.orig/include/linux/i2c-algo-bit.h 2009-06-10 05:05:27.000000000 +0200
> +++ linux-2.6.34-rc1/include/linux/i2c-algo-bit.h 2010-03-09 18:53:06.000000000 +0100
> @@ -32,6 +32,8 @@
> */
> struct i2c_algo_bit_data {
> void *data; /* private data for lowlevel routines */
> + int (*pre_xfer) (struct i2c_adapter *i2c_adap, void *data);
> + void (*post_xfer) (struct i2c_adapter *i2c_adap, void *data);
> void (*setsda) (void *data, int state);
> void (*setscl) (void *data, int state);
> int (*getsda) (void *data);
>
> Would it help?
This patch seems works fine. I've updated the radeon driver to
register a bit algo adapter if the i2c line is not hw capable. I'll
send out updated radeon patches today or tomorrow once I've given it
further testing.
Alex
>
>> Right now we use
>> bit-algo i2c for the ddc buses, but they won't work externally to the
>> driver without the proper gpio masking prior to using them. In the
>> radeon-algo patches, I use bit algo internally when I cannot use the
>> hardware i2c engines, or in cases where I haven't implemented support
>> yet for the hardware engine (as most gpios can be driven by sw or the
>> hw engine). The problem is, this exposes the i2c bit-algo buses as
>> well as the radeon-algo buses.
>
> This is bad, as it defeats the slave address uniqueness mechanism. Bad
> things could happen. Would the patch above be sufficient to solve your
> case?
>
>> Is there a way to not expose the bit-algo buses that are used
>> internally?
>
> No, this is not possible at the time being. That being said, it
> shouldn't be difficult, if the need exists. Looking at i2c-algo-bit,
> the registration part is split into a preparation step and the actual
> registration with i2c-core. The preparation step if done by
> i2c_bit_prepare_bus(). If we exported this function, then you could
> easily call it to create an internal i2c-algo-bit-based adapter, which
> you wouldn't have to register if you don't want to:
>
> From: Jean Delvare <khali@xxxxxxxxxxxx>
> Subject: i2c-algo-bit: Export i2c_bit_prepare_bus
>
> This lets drivers make use of the i2c-algo-bit implementation without
> actually registering the i2c adapter in question. This is useful to
> drivers which need more than the i2c-algo-bit driver offers.
>
> Signed-off-by: Jean Delvare <khali@xxxxxxxxxxxx>
> ---
> drivers/i2c/algos/i2c-algo-bit.c | 3 ++-
> include/linux/i2c-algo-bit.h | 1 +
> 2 files changed, 3 insertions(+), 1 deletion(-)
>
> --- linux-2.6.34-rc1.orig/drivers/i2c/algos/i2c-algo-bit.c 2010-03-10 08:09:03.000000000 +0100
> +++ linux-2.6.34-rc1/drivers/i2c/algos/i2c-algo-bit.c 2010-03-10 10:23:51.000000000 +0100
> @@ -601,7 +601,7 @@ static const struct i2c_algorithm i2c_bi
> /*
> * registering functions to load algorithms at runtime
> */
> -static int i2c_bit_prepare_bus(struct i2c_adapter *adap)
> +int i2c_bit_prepare_bus(struct i2c_adapter *adap)
> {
> struct i2c_algo_bit_data *bit_adap = adap->algo_data;
>
> @@ -617,6 +617,7 @@ static int i2c_bit_prepare_bus(struct i2
>
> return 0;
> }
> +EXPORT_SYMBOL(i2c_bit_prepare_bus);
>
> int i2c_bit_add_bus(struct i2c_adapter *adap)
> {
> --- linux-2.6.34-rc1.orig/include/linux/i2c-algo-bit.h 2010-03-10 08:09:03.000000000 +0100
> +++ linux-2.6.34-rc1/include/linux/i2c-algo-bit.h 2010-03-10 10:24:03.000000000 +0100
> @@ -47,6 +47,7 @@ struct i2c_algo_bit_data {
> int timeout; /* in jiffies */
> };
>
> +int i2c_bit_prepare_bus(struct i2c_adapter *);
> int i2c_bit_add_bus(struct i2c_adapter *);
> int i2c_bit_add_numbered_bus(struct i2c_adapter *);
>
>
> With this possibility, I guess you wouldn't even need the first patch
> any longer? If both are needed, that's fine with me, but if only one is
> needed, that's even better.
>
>> I've attached the patches for reference.
>
> Please let me know if either or both of my 2 proposals above fit your
> needs.
>
> --
> Jean Delvare
>
--
To unsubscribe from this list: send the line "unsubscribe linux-i2c" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
