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?
> 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
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