[RFC 00/11] i2c: add generic quirk infrastructure

[RFC 00/11] i2c: add generic quirk infrastructure

[Wolfram Sang]

Recently, a number of submitted I2C master drivers could not fully handle all
I2C type transfers due to limited HW. So, they had to bail out with some errno
although the user supplied a valid I2C transfer. In order to centralize such
quirks, a central structure describing the quirks is introduced. The next patch
lets the core do the checks based on the information about the quirks. Then
existing drivers with quirks are converted.

This already has the advantage of avoiding code duplication and having
consistent error handling. Later, once the structure is tested and stable, we
can pass it over to the users, so they can actually check what the current HW
is capable of and react accordingly.

These patches are RFC and only build-tested so far. Yet, I wanted to show what
I am up to. I will do some testing on HW once I finished my task of fixing the
slave interface, hopefully after next week.

I'd really love to see this go into v3.20, but this will need assistance. I
really need testers, at least for the recent hardware. Other comments/reviews
are also appreciated.

Patches are based on v3.19-rc3 and the branch is here

git://git.kernel.org/pub/scm/linux/kernel/git/wsa/linux.git i2c/quirks

Thanks,

   Wolfram


Wolfram Sang (11):
  i2c: add quirk structure to describe adapter flaws
  i2c: add quirk checks to core
  i2c: at91: make use of the new infrastructure for quirks
  i2c: opal: make use of the new infrastructure for quirks
  i2c: qup: make use of the new infrastructure for quirks
  i2c: cpm: make use of the new infrastructure for quirks
  i2c: axxia: make use of the new infrastructure for quirks
  i2c: dln2: make use of the new infrastructure for quirks
  i2c: powermac: make use of the new infrastructure for quirks
  i2c: viperboard: make use of the new infrastructure for quirks
  i2c: pmcmsp: make use of the new infrastructure for quirks

 drivers/i2c/busses/i2c-at91.c       | 32 ++++++++--------------
 drivers/i2c/busses/i2c-axxia.c      | 11 ++++----
 drivers/i2c/busses/i2c-cpm.c        | 20 +++++++-------
 drivers/i2c/busses/i2c-dln2.c       | 12 ++++-----
 drivers/i2c/busses/i2c-opal.c       | 22 +++++++--------
 drivers/i2c/busses/i2c-pmcmsp.c     | 42 +++++++++++------------------
 drivers/i2c/busses/i2c-powermac.c   | 10 +++----
 drivers/i2c/busses/i2c-qup.c        | 21 +++++++--------
 drivers/i2c/busses/i2c-viperboard.c | 10 ++++---
 drivers/i2c/i2c-core.c              | 53 +++++++++++++++++++++++++++++++++++++
 include/linux/i2c.h                 | 35 ++++++++++++++++++++++++
 11 files changed, 167 insertions(+), 101 deletions(-)

-- 
2.1.3

[RFC 01/11] i2c: add quirk structure to describe adapter flaws

[Wolfram Sang]

The number of I2C adapters which are not fully I2C compatible is rising,
sadly. Drivers usually do handle the flaws, still the user receives only
some errno for a transfer which normally can be expected to work. This
patch introduces a formal description of flaws. One advantage is that
the core can check before the actual transfer if the messages could be
transferred at all. This is done in the next patch. Another advantage is
that we can pass this information to the user so the restrictions are
exactly known and further actions can be based on that. This will be
done later after some stabilization period for this description.

Signed-off-by: Wolfram Sang <wsa-z923LK4zBo2bacvFa/9K2g@public.gmane.org>
---
 include/linux/i2c.h | 35 +++++++++++++++++++++++++++++++++++
 1 file changed, 35 insertions(+)

diff --git a/include/linux/i2c.h b/include/linux/i2c.h
index e3a1721c8354..f8a642713706 100644
--- a/include/linux/i2c.h
+++ b/include/linux/i2c.h
@@ -447,6 +447,40 @@ int i2c_recover_bus(struct i2c_adapter *adap);
 int i2c_generic_gpio_recovery(struct i2c_adapter *adap);
 int i2c_generic_scl_recovery(struct i2c_adapter *adap);
 
+/**
+ * struct i2c_adapter_quirks - describe flaws of an i2c adapter
+ * @flags: see I2C_ADAPTER_QUIRK_* for possible flags
+ * @max_num_msgs: maximum number of messages per transfer
+ * @max_write_len: maximum length of a write message
+ * @max_read_len: maximum length of a read message
+ * @max_comb_write_len: maximum length of a write in a combined message
+ * @max_comb_read_len: maximum length of a read in a combined message
+ *
+ * Note about combined messages: Some I2C controllers can only send one
+ * message per transfer, plus something called combined message or
+ * write-then-read. This is a (usually) small write message followed by
+ * a read message and barely enough to access register based slaves like
+ * EEPROMs. There is a flag to support this mode. It implies max_num_msg = 2
+ * and does the length checks with max_comb_*_len because combined message mode
+ * usually has its own limitations. Read/write flags of the messages are also
+ * checked to be proper. Because of HW implementation, some controllers can
+ * actually do write-then-anything. To support that, write-then-read has been
+ * broken out into write-first and read-second.
+ */
+struct i2c_adapter_quirks {
+	u64 flags;
+	int max_num_msgs;
+	u16 max_write_len;
+	u16 max_read_len;
+	u16 max_comb_write_len;
+	u16 max_comb_read_len;
+};
+
+#define I2C_ADAPTER_QUIRK_COMB_WRITE_FIRST	BIT(0)
+#define I2C_ADAPTER_QUIRK_COMB_READ_SECOND	BIT(1)
+#define I2C_ADAPTER_QUIRK_COMB_WRITE_THEN_READ	(I2C_ADAPTER_QUIRK_COMB_WRITE_FIRST | \
+						I2C_ADAPTER_QUIRK_COMB_READ_SECOND)
+
 /*
  * i2c_adapter is the structure used to identify a physical i2c bus along
  * with the access algorithms necessary to access it.
@@ -472,6 +506,7 @@ struct i2c_adapter {
 	struct list_head userspace_clients;
 
 	struct i2c_bus_recovery_info *bus_recovery_info;
+	struct i2c_adapter_quirks *quirks;
 };
 #define to_i2c_adapter(d) container_of(d, struct i2c_adapter, dev)
 
-- 
2.1.3

Re: [RFC 01/11] i2c: add quirk structure to describe adapter flaws

[Eddie Huang]

Hi Wolfram,

On Fri, 2015-01-09 at 18:21 +0100, Wolfram Sang wrote:
>  
> + */
> +struct i2c_adapter_quirks {
> +	u64 flags;
> +	int max_num_msgs;
> +	u16 max_write_len;
> +	u16 max_read_len;
> +	u16 max_comb_write_len;
> +	u16 max_comb_read_len;
> +};
> +
> +#define I2C_ADAPTER_QUIRK_COMB_WRITE_FIRST	BIT(0)
> +#define I2C_ADAPTER_QUIRK_COMB_READ_SECOND	BIT(1)
> +#define I2C_ADAPTER_QUIRK_COMB_WRITE_THEN_READ	(I2C_ADAPTER_QUIRK_COMB_WRITE_FIRST | \
> +						I2C_ADAPTER_QUIRK_COMB_READ_SECOND)
> +
>  /*
>   * i2c_adapter is the structure used to identify a physical i2c bus along
>   * with the access algorithms necessary to access it.
> @@ -472,6 +506,7 @@ struct i2c_adapter {
>  	struct list_head userspace_clients;
>  
>  	struct i2c_bus_recovery_info *bus_recovery_info;
> +	struct i2c_adapter_quirks *quirks;
>  };
>  #define to_i2c_adapter(d) container_of(d, struct i2c_adapter, dev)
>  

I suggest to add const.
	const struct i2c_adapter_quirks *quirks;

also, in i2c-core.c, should modify:
	const struct i2c_adapter_quirks *q = adap->quirks;

Re: [RFC 01/11] i2c: add quirk structure to describe adapter flaws

[Wolfram Sang]

[-- Attachment #1: Type: text/plain, Size: 341 bytes --]


> > +	struct i2c_adapter_quirks *quirks;
> >  };
> >  #define to_i2c_adapter(d) container_of(d, struct i2c_adapter, dev)
> >  
> 
> I suggest to add const.
> 	const struct i2c_adapter_quirks *quirks;
> 
> also, in i2c-core.c, should modify:
> 	const struct i2c_adapter_quirks *q = adap->quirks;

Thanks, I'll think about it.


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Re: [RFC 01/11] i2c: add quirk structure to describe adapter flaws

[Wolfram Sang]

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On Mon, Jan 19, 2015 at 04:05:15PM +0100, Wolfram Sang wrote:
> 
> > > +	struct i2c_adapter_quirks *quirks;
> > >  };
> > >  #define to_i2c_adapter(d) container_of(d, struct i2c_adapter, dev)
> > >  
> > 
> > I suggest to add const.
> > 	const struct i2c_adapter_quirks *quirks;
> > 
> > also, in i2c-core.c, should modify:
> > 	const struct i2c_adapter_quirks *q = adap->quirks;
> 
> Thanks, I'll think about it.

And added it...


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Re: [RFC 01/11] i2c: add quirk structure to describe adapter flaws

[Yingjoe Chen]

On Fri, 2015-01-09 at 18:21 +0100, Wolfram Sang wrote:
> The number of I2C adapters which are not fully I2C compatible is rising,
> sadly. Drivers usually do handle the flaws, still the user receives only
> some errno for a transfer which normally can be expected to work. This
> patch introduces a formal description of flaws. One advantage is that
> the core can check before the actual transfer if the messages could be
> transferred at all. This is done in the next patch. Another advantage is
> that we can pass this information to the user so the restrictions are
> exactly known and further actions can be based on that. This will be
> done later after some stabilization period for this description.

Hi Wolfram,

This can describe the behavior of our current upstream driver[1], which
only support combine write-then-read.

After checking with Xudong & HW guys, it seems our HW can do more. 
On MT8135, it can support at most 2 messages, no matter read or write,
with the limitation that the length of the second message must <=
31bytes.

So this RFC is enough for our driver, but it would be better if we could
also support other case.

Joe.C

[1]:
http://lists.infradead.org/pipermail/linux-arm-kernel/2014-November/305468.html

Re: [RFC 01/11] i2c: add quirk structure to describe adapter flaws

[Wolfram Sang]

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Hi,

> This can describe the behavior of our current upstream driver[1], which
> only support combine write-then-read.
> 
> After checking with Xudong & HW guys, it seems our HW can do more. 
> On MT8135, it can support at most 2 messages, no matter read or write,
> with the limitation that the length of the second message must <=
> 31bytes.
> 
> So this RFC is enough for our driver, but it would be better if we could
> also support other case.

Hmm, I think we can convert max_comb_{read|write}_len to
max_comb_{1st|2nd}_msg_len or similar.

I'll check but it will probably not before next week.

Thanks for the input!


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[RFC 02/11] i2c: add quirk checks to core

[Wolfram Sang]

Let the core do the checks if HW quirks prevent a transfer. Saves code
from drivers and adds consistency.

Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
---
 drivers/i2c/i2c-core.c | 53 ++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 53 insertions(+)

diff --git a/drivers/i2c/i2c-core.c b/drivers/i2c/i2c-core.c
index 39d25a8cb1ad..7b10a19abf5b 100644
--- a/drivers/i2c/i2c-core.c
+++ b/drivers/i2c/i2c-core.c
@@ -2063,6 +2063,56 @@ module_exit(i2c_exit);
  * ----------------------------------------------------
  */
 
+/* Check if val is exceeding the quirk IFF quirk is non 0 */
+#define i2c_quirk_exceeded(val, quirk) ((quirk) && ((val) > (quirk)))
+
+static int i2c_quirk_error(struct i2c_adapter *adap, struct i2c_msg *msg, char *err_msg)
+{
+	dev_err(&adap->dev, "quirk: %s (addr 0x%04x, size %u)\n", err_msg, msg->addr, msg->len);
+	return -EOPNOTSUPP;
+}
+
+static int i2c_check_for_quirks(struct i2c_adapter *adap, struct i2c_msg *msgs, int num)
+{
+	struct i2c_adapter_quirks *q = adap->quirks;
+	u16 max_read = q->max_read_len, max_write = q->max_write_len;
+	int max_num = q->max_num_msgs, i;
+
+	if (q->flags & I2C_ADAPTER_QUIRK_COMB_WRITE_THEN_READ)
+		max_num = 2;
+
+	if (i2c_quirk_exceeded(num, max_num))
+		return i2c_quirk_error(adap, &msgs[0], "too many messages");
+
+	if (num == 2 && q->flags & I2C_ADAPTER_QUIRK_COMB_WRITE_FIRST) {
+		if (msgs[0].flags & I2C_M_RD)
+			return i2c_quirk_error(adap, &msgs[0], "invalid first write msg");
+
+		max_write = q->max_comb_write_len;
+	}
+
+	if (num == 2 && q->flags & I2C_ADAPTER_QUIRK_COMB_READ_SECOND) {
+		if (!(msgs[1].flags & I2C_M_RD) || msgs[0].addr != msgs[1].addr)
+			return i2c_quirk_error(adap, &msgs[1], "invalid second read msg");
+
+		max_read = q->max_comb_read_len;
+	}
+
+	for (i = 0; i < num; i++) {
+		u16 len = msgs[i].len;
+
+		if (msgs[i].flags & I2C_M_RD) {
+			if (i2c_quirk_exceeded(len, max_read))
+				return i2c_quirk_error(adap, &msgs[i], "msg too long");
+		} else {
+			if (i2c_quirk_exceeded(len, max_write))
+				return i2c_quirk_error(adap, &msgs[i], "msg too long");
+		}
+	}
+
+	return 0;
+}
+
 /**
  * __i2c_transfer - unlocked flavor of i2c_transfer
  * @adap: Handle to I2C bus
@@ -2080,6 +2130,9 @@ int __i2c_transfer(struct i2c_adapter *adap, struct i2c_msg *msgs, int num)
 	unsigned long orig_jiffies;
 	int ret, try;
 
+	if (adap->quirks && i2c_check_for_quirks(adap, msgs, num))
+		return -EOPNOTSUPP;
+
 	/* i2c_trace_msg gets enabled when tracepoint i2c_transfer gets
 	 * enabled.  This is an efficient way of keeping the for-loop from
 	 * being executed when not needed.
-- 
2.1.3

Re: [RFC 02/11] i2c: add quirk checks to core

[Sergei Shtylyov]

Hello.

On 01/09/2015 08:21 PM, Wolfram Sang wrote:

> Let the core do the checks if HW quirks prevent a transfer. Saves code
> from drivers and adds consistency.

> Signed-off-by: Wolfram Sang <wsa-z923LK4zBo2bacvFa/9K2g@public.gmane.org>
> ---
>   drivers/i2c/i2c-core.c | 53 ++++++++++++++++++++++++++++++++++++++++++++++++++
>   1 file changed, 53 insertions(+)
>
> diff --git a/drivers/i2c/i2c-core.c b/drivers/i2c/i2c-core.c
> index 39d25a8cb1ad..7b10a19abf5b 100644
> --- a/drivers/i2c/i2c-core.c
> +++ b/drivers/i2c/i2c-core.c
> @@ -2063,6 +2063,56 @@ module_exit(i2c_exit);
>    * ----------------------------------------------------
>    */
>
> +/* Check if val is exceeding the quirk IFF quirk is non 0 */
> +#define i2c_quirk_exceeded(val, quirk) ((quirk) && ((val) > (quirk)))
> +
> +static int i2c_quirk_error(struct i2c_adapter *adap, struct i2c_msg *msg, char *err_msg)
> +{
> +	dev_err(&adap->dev, "quirk: %s (addr 0x%04x, size %u)\n", err_msg, msg->addr, msg->len);
> +	return -EOPNOTSUPP;
> +}

    Always returning the same value doesn't make much sense. Are you trying to 
save space on the call sites?

[...]
> @@ -2080,6 +2130,9 @@ int __i2c_transfer(struct i2c_adapter *adap, struct i2c_msg *msgs, int num)
>   	unsigned long orig_jiffies;
>   	int ret, try;
>
> +	if (adap->quirks && i2c_check_for_quirks(adap, msgs, num))

    So, you only check for non-zero result of this function? Perhaps it makes 
sense to return true/false instead?

> +		return -EOPNOTSUPP;
> +

WBR, Sergei

Re: [RFC 02/11] i2c: add quirk checks to core

[Wolfram Sang]

[-- Attachment #1: Type: text/plain, Size: 1820 bytes --]

On Fri, Jan 09, 2015 at 10:35:27PM +0300, Sergei Shtylyov wrote:
> Hello.
> 
> On 01/09/2015 08:21 PM, Wolfram Sang wrote:
> 
> >Let the core do the checks if HW quirks prevent a transfer. Saves code
> >from drivers and adds consistency.
> 
> >Signed-off-by: Wolfram Sang <wsa-z923LK4zBo2bacvFa/9K2g@public.gmane.org>
> >---
> >  drivers/i2c/i2c-core.c | 53 ++++++++++++++++++++++++++++++++++++++++++++++++++
> >  1 file changed, 53 insertions(+)
> >
> >diff --git a/drivers/i2c/i2c-core.c b/drivers/i2c/i2c-core.c
> >index 39d25a8cb1ad..7b10a19abf5b 100644
> >--- a/drivers/i2c/i2c-core.c
> >+++ b/drivers/i2c/i2c-core.c
> >@@ -2063,6 +2063,56 @@ module_exit(i2c_exit);
> >   * ----------------------------------------------------
> >   */
> >
> >+/* Check if val is exceeding the quirk IFF quirk is non 0 */
> >+#define i2c_quirk_exceeded(val, quirk) ((quirk) && ((val) > (quirk)))
> >+
> >+static int i2c_quirk_error(struct i2c_adapter *adap, struct i2c_msg *msg, char *err_msg)
> >+{
> >+	dev_err(&adap->dev, "quirk: %s (addr 0x%04x, size %u)\n", err_msg, msg->addr, msg->len);
> >+	return -EOPNOTSUPP;
> >+}
> 
>    Always returning the same value doesn't make much sense. Are you trying
> to save space on the call sites?

Please elaborate. I think it does. If a quirk matches, we report that we
don't support this transfer.

> [...]
> >@@ -2080,6 +2130,9 @@ int __i2c_transfer(struct i2c_adapter *adap, struct i2c_msg *msgs, int num)
> >  	unsigned long orig_jiffies;
> >  	int ret, try;
> >
> >+	if (adap->quirks && i2c_check_for_quirks(adap, msgs, num))
> 
>    So, you only check for non-zero result of this function? Perhaps it makes
> sense to return true/false instead?

Could be done, but what would be the advantage? A lot of functions
return errno or 0.


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Re: [RFC 02/11] i2c: add quirk checks to core

[Sergei Shtylyov]

Hello.

On 01/09/2015 11:45 PM, Wolfram Sang wrote:

>>> Let the core do the checks if HW quirks prevent a transfer. Saves code
>> >from drivers and adds consistency.

>>> Signed-off-by: Wolfram Sang <wsa-z923LK4zBo2bacvFa/9K2g@public.gmane.org>
>>> ---
>>>   drivers/i2c/i2c-core.c | 53 ++++++++++++++++++++++++++++++++++++++++++++++++++
>>>   1 file changed, 53 insertions(+)
>>>
>>> diff --git a/drivers/i2c/i2c-core.c b/drivers/i2c/i2c-core.c
>>> index 39d25a8cb1ad..7b10a19abf5b 100644
>>> --- a/drivers/i2c/i2c-core.c
>>> +++ b/drivers/i2c/i2c-core.c
>>> @@ -2063,6 +2063,56 @@ module_exit(i2c_exit);
>>>    * ----------------------------------------------------
>>>    */
>>>
>>> +/* Check if val is exceeding the quirk IFF quirk is non 0 */
>>> +#define i2c_quirk_exceeded(val, quirk) ((quirk) && ((val) > (quirk)))
>>> +
>>> +static int i2c_quirk_error(struct i2c_adapter *adap, struct i2c_msg *msg, char *err_msg)
>>> +{
>>> +	dev_err(&adap->dev, "quirk: %s (addr 0x%04x, size %u)\n", err_msg, msg->addr, msg->len);
>>> +	return -EOPNOTSUPP;
>>> +}

>>     Always returning the same value doesn't make much sense. Are you trying
>> to save space on the call sites?

> Please elaborate. I think it does. If a quirk matches, we report that we
> don't support this transfer.

    OK, but what's the point of having this function return *int* if it always 
returns the same value? AFAIU, you're trying to save the code space on the 
call sites of this function by not having *return* -EOPNOTSUPP there each time?

>> [...]
>>> @@ -2080,6 +2130,9 @@ int __i2c_transfer(struct i2c_adapter *adap, struct i2c_msg *msgs, int num)
>>>   	unsigned long orig_jiffies;
>>>   	int ret, try;
>>>
>>> +	if (adap->quirks && i2c_check_for_quirks(adap, msgs, num))

>>     So, you only check for non-zero result of this function? Perhaps it makes
>> sense to return true/false instead?

> Could be done, but what would be the advantage? A lot of functions
> return errno or 0.

    It would have been OK if you were actually caring about the result, e.g. 
returning it from __i2c_transfer(). Since you don't, IMO it would make more 
sense to return true from i2c_check_for_quirks() (making it *bool*) iff it did 
find/apply a quirk.

WBR, Sergei

Re: [RFC 02/11] i2c: add quirk checks to core

[Ludovic Desroches]

Hi Wolfram,

On Fri, Jan 09, 2015 at 06:21:32PM +0100, Wolfram Sang wrote:
> Let the core do the checks if HW quirks prevent a transfer. Saves code
> from drivers and adds consistency.
> 
> Signed-off-by: Wolfram Sang <wsa-z923LK4zBo2bacvFa/9K2g@public.gmane.org>
> ---
>  drivers/i2c/i2c-core.c | 53 ++++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 53 insertions(+)
> 
> diff --git a/drivers/i2c/i2c-core.c b/drivers/i2c/i2c-core.c
> index 39d25a8cb1ad..7b10a19abf5b 100644
> --- a/drivers/i2c/i2c-core.c
> +++ b/drivers/i2c/i2c-core.c
> @@ -2063,6 +2063,56 @@ module_exit(i2c_exit);
>   * ----------------------------------------------------
>   */
>  
> +/* Check if val is exceeding the quirk IFF quirk is non 0 */
> +#define i2c_quirk_exceeded(val, quirk) ((quirk) && ((val) > (quirk)))
> +
> +static int i2c_quirk_error(struct i2c_adapter *adap, struct i2c_msg *msg, char *err_msg)
> +{
> +	dev_err(&adap->dev, "quirk: %s (addr 0x%04x, size %u)\n", err_msg, msg->addr, msg->len);
> +	return -EOPNOTSUPP;
> +}
> +
> +static int i2c_check_for_quirks(struct i2c_adapter *adap, struct i2c_msg *msgs, int num)
> +{
> +	struct i2c_adapter_quirks *q = adap->quirks;
> +	u16 max_read = q->max_read_len, max_write = q->max_write_len;
> +	int max_num = q->max_num_msgs, i;
> +
> +	if (q->flags & I2C_ADAPTER_QUIRK_COMB_WRITE_THEN_READ)
> +		max_num = 2;
> +
> +	if (i2c_quirk_exceeded(num, max_num))
> +		return i2c_quirk_error(adap, &msgs[0], "too many messages");
> +
> +	if (num == 2 && q->flags & I2C_ADAPTER_QUIRK_COMB_WRITE_FIRST) {
> +		if (msgs[0].flags & I2C_M_RD)
> +			return i2c_quirk_error(adap, &msgs[0], "invalid first write msg");
> +
> +		max_write = q->max_comb_write_len;
> +	}
> +
> +	if (num == 2 && q->flags & I2C_ADAPTER_QUIRK_COMB_READ_SECOND) {
> +		if (!(msgs[1].flags & I2C_M_RD) || msgs[0].addr != msgs[1].addr)
> +			return i2c_quirk_error(adap, &msgs[1], "invalid second read msg");
> +
> +		max_read = q->max_comb_read_len;
> +	}
> +
> +	for (i = 0; i < num; i++) {
> +		u16 len = msgs[i].len;
> +
> +		if (msgs[i].flags & I2C_M_RD) {
> +			if (i2c_quirk_exceeded(len, max_read))
> +				return i2c_quirk_error(adap, &msgs[i], "msg too long");
> +		} else {
> +			if (i2c_quirk_exceeded(len, max_write))
> +				return i2c_quirk_error(adap, &msgs[i], "msg too long");
> +		}
> +	}
> +

I am not sure it will perfectly fit at91 quirks.

The hardware can handle two messages by using the internal address
feature. The internal address size is from one byte to three bytes. Then
the length of the first message is limited to three but we don't have
this constraint for the second one. If we have 'write then read' no problem
but if we have two write messages, the second one will cause a quirk
exceeded error.

Regards

Ludovic

> +	return 0;
> +}
> +
>  /**
>   * __i2c_transfer - unlocked flavor of i2c_transfer
>   * @adap: Handle to I2C bus
> @@ -2080,6 +2130,9 @@ int __i2c_transfer(struct i2c_adapter *adap, struct i2c_msg *msgs, int num)
>  	unsigned long orig_jiffies;
>  	int ret, try;
>  
> +	if (adap->quirks && i2c_check_for_quirks(adap, msgs, num))
> +		return -EOPNOTSUPP;
> +
>  	/* i2c_trace_msg gets enabled when tracepoint i2c_transfer gets
>  	 * enabled.  This is an efficient way of keeping the for-loop from
>  	 * being executed when not needed.
> -- 
> 2.1.3
> 

Re: [RFC 02/11] i2c: add quirk checks to core

[Wolfram Sang]

[-- Attachment #1: Type: text/plain, Size: 748 bytes --]


> I am not sure it will perfectly fit at91 quirks.

I think it does.

> The hardware can handle two messages by using the internal address
> feature. The internal address size is from one byte to three bytes. Then
> the length of the first message is limited to three but we don't have
> this constraint for the second one. If we have 'write then read' no problem
> but if we have two write messages, the second one will cause a quirk
> exceeded error.

Yeah, for this reason I seperated I2C_ADAPTER_QUIRK_COMB_WRITE_FIRST
out. The first message is checked against max_comb_write_len which is
set to 3 for your driver. The second is checked agains max_write_len
which is unset in your driver and thus can be of any length.

That should work, no?


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Re: [RFC 02/11] i2c: add quirk checks to core

[Russell King - ARM Linux]

On Fri, Jan 09, 2015 at 06:21:32PM +0100, Wolfram Sang wrote:
> +static int i2c_quirk_error(struct i2c_adapter *adap, struct i2c_msg *msg, char *err_msg)
> +{
> +	dev_err(&adap->dev, "quirk: %s (addr 0x%04x, size %u)\n", err_msg, msg->addr, msg->len);
> +	return -EOPNOTSUPP;
> +}

So, what happens if I open an I2C adapter, find a message which causes
i2c_quirk_error() to be called, and then spin repeatedly calling that...
Shouldn't there be some rate limiting to this?

-- 
FTTC broadband for 0.8mile line: currently at 10.5Mbps down 400kbps up
according to speedtest.net.

Re: [RFC 02/11] i2c: add quirk checks to core

[Wolfram Sang]

[-- Attachment #1: Type: text/plain, Size: 640 bytes --]

On Mon, Jan 12, 2015 at 12:08:14PM +0000, Russell King - ARM Linux wrote:
> On Fri, Jan 09, 2015 at 06:21:32PM +0100, Wolfram Sang wrote:
> > +static int i2c_quirk_error(struct i2c_adapter *adap, struct i2c_msg *msg, char *err_msg)
> > +{
> > +	dev_err(&adap->dev, "quirk: %s (addr 0x%04x, size %u)\n", err_msg, msg->addr, msg->len);
> > +	return -EOPNOTSUPP;
> > +}
> 
> So, what happens if I open an I2C adapter, find a message which causes
> i2c_quirk_error() to be called, and then spin repeatedly calling that...
> Shouldn't there be some rate limiting to this?

Can be argued. Changed to dev_err_ratelimited(). Thanks!


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Re: [RFC 02/11] i2c: add quirk checks to core

[Matthias Brugger]

2015-01-09 18:21 GMT+01:00 Wolfram Sang <wsa-z923LK4zBo2bacvFa/9K2g@public.gmane.org>:
> Let the core do the checks if HW quirks prevent a transfer. Saves code
> from drivers and adds consistency.
>
> Signed-off-by: Wolfram Sang <wsa-z923LK4zBo2bacvFa/9K2g@public.gmane.org>
> ---
>  drivers/i2c/i2c-core.c | 53 ++++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 53 insertions(+)
>
> diff --git a/drivers/i2c/i2c-core.c b/drivers/i2c/i2c-core.c
> index 39d25a8cb1ad..7b10a19abf5b 100644
> --- a/drivers/i2c/i2c-core.c
> +++ b/drivers/i2c/i2c-core.c
> @@ -2063,6 +2063,56 @@ module_exit(i2c_exit);
>   * ----------------------------------------------------
>   */
>
> +/* Check if val is exceeding the quirk IFF quirk is non 0 */
> +#define i2c_quirk_exceeded(val, quirk) ((quirk) && ((val) > (quirk)))
> +
> +static int i2c_quirk_error(struct i2c_adapter *adap, struct i2c_msg *msg, char *err_msg)
> +{
> +       dev_err(&adap->dev, "quirk: %s (addr 0x%04x, size %u)\n", err_msg, msg->addr, msg->len);
> +       return -EOPNOTSUPP;
> +}
> +
> +static int i2c_check_for_quirks(struct i2c_adapter *adap, struct i2c_msg *msgs, int num)
> +{
> +       struct i2c_adapter_quirks *q = adap->quirks;
> +       u16 max_read = q->max_read_len, max_write = q->max_write_len;
> +       int max_num = q->max_num_msgs, i;
> +
> +       if (q->flags & I2C_ADAPTER_QUIRK_COMB_WRITE_THEN_READ)
> +               max_num = 2;
> +
> +       if (i2c_quirk_exceeded(num, max_num))
> +               return i2c_quirk_error(adap, &msgs[0], "too many messages");
> +
> +       if (num == 2 && q->flags & I2C_ADAPTER_QUIRK_COMB_WRITE_FIRST) {
> +               if (msgs[0].flags & I2C_M_RD)
> +                       return i2c_quirk_error(adap, &msgs[0], "invalid first write msg");
> +
> +               max_write = q->max_comb_write_len;
> +       }
> +
> +       if (num == 2 && q->flags & I2C_ADAPTER_QUIRK_COMB_READ_SECOND) {
> +               if (!(msgs[1].flags & I2C_M_RD) || msgs[0].addr != msgs[1].addr)
> +                       return i2c_quirk_error(adap, &msgs[1], "invalid second read msg");
> +
> +               max_read = q->max_comb_read_len;
> +       }
> +
> +       for (i = 0; i < num; i++) {
> +               u16 len = msgs[i].len;
> +
> +               if (msgs[i].flags & I2C_M_RD) {
> +                       if (i2c_quirk_exceeded(len, max_read))
> +                               return i2c_quirk_error(adap, &msgs[i], "msg too long");
> +               } else {
> +                       if (i2c_quirk_exceeded(len, max_write))
> +                               return i2c_quirk_error(adap, &msgs[i], "msg too long");
> +               }

What about being more verbose in the error message, specifying if it
was a read or a write message that failed?

> +       }
> +
> +       return 0;
> +}
> +
>  /**
>   * __i2c_transfer - unlocked flavor of i2c_transfer
>   * @adap: Handle to I2C bus
> @@ -2080,6 +2130,9 @@ int __i2c_transfer(struct i2c_adapter *adap, struct i2c_msg *msgs, int num)
>         unsigned long orig_jiffies;
>         int ret, try;
>
> +       if (adap->quirks && i2c_check_for_quirks(adap, msgs, num))
> +               return -EOPNOTSUPP;
> +
>         /* i2c_trace_msg gets enabled when tracepoint i2c_transfer gets
>          * enabled.  This is an efficient way of keeping the for-loop from
>          * being executed when not needed.
> --
> 2.1.3
>
>
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel



-- 
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Re: [RFC 02/11] i2c: add quirk checks to core

[Wolfram Sang]

[-- Attachment #1: Type: text/plain, Size: 581 bytes --]


> > +               if (msgs[i].flags & I2C_M_RD) {
> > +                       if (i2c_quirk_exceeded(len, max_read))
> > +                               return i2c_quirk_error(adap, &msgs[i], "msg too long");
> > +               } else {
> > +                       if (i2c_quirk_exceeded(len, max_write))
> > +                               return i2c_quirk_error(adap, &msgs[i], "msg too long");
> > +               }
> 
> What about being more verbose in the error message, specifying if it
> was a read or a write message that failed?

Yes, done now. Thanks!


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[RFC 03/11] i2c: at91: make use of the new infrastructure for quirks

[Wolfram Sang]

Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
---
 drivers/i2c/busses/i2c-at91.c | 32 +++++++++++---------------------
 1 file changed, 11 insertions(+), 21 deletions(-)

diff --git a/drivers/i2c/busses/i2c-at91.c b/drivers/i2c/busses/i2c-at91.c
index 636fd2efad88..8be7cf6e2747 100644
--- a/drivers/i2c/busses/i2c-at91.c
+++ b/drivers/i2c/busses/i2c-at91.c
@@ -487,30 +487,10 @@ static int at91_twi_xfer(struct i2c_adapter *adap, struct i2c_msg *msg, int num)
 	if (ret < 0)
 		goto out;
 
-	/*
-	 * The hardware can handle at most two messages concatenated by a
-	 * repeated start via it's internal address feature.
-	 */
-	if (num > 2) {
-		dev_err(dev->dev,
-			"cannot handle more than two concatenated messages.\n");
-		ret = 0;
-		goto out;
-	} else if (num == 2) {
+	if (num == 2) {
 		int internal_address = 0;
 		int i;
 
-		if (msg->flags & I2C_M_RD) {
-			dev_err(dev->dev, "first transfer must be write.\n");
-			ret = -EINVAL;
-			goto out;
-		}
-		if (msg->len > 3) {
-			dev_err(dev->dev, "first message size must be <= 3.\n");
-			ret = -EINVAL;
-			goto out;
-		}
-
 		/* 1st msg is put into the internal address, start with 2nd */
 		m_start = &msg[1];
 		for (i = 0; i < msg->len; ++i) {
@@ -540,6 +520,15 @@ out:
 	return ret;
 }
 
+/*
+ * The hardware can handle at most two messages concatenated by a
+ * repeated start via it's internal address feature.
+ */
+static struct i2c_adapter_quirks at91_twi_quirks = {
+	.flags = I2C_ADAPTER_QUIRK_COMB_WRITE_FIRST,
+	.max_comb_write_len = 3,
+};
+
 static u32 at91_twi_func(struct i2c_adapter *adapter)
 {
 	return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL
@@ -777,6 +766,7 @@ static int at91_twi_probe(struct platform_device *pdev)
 	dev->adapter.owner = THIS_MODULE;
 	dev->adapter.class = I2C_CLASS_DEPRECATED;
 	dev->adapter.algo = &at91_twi_algorithm;
+	dev->adapter.quirks = &at91_twi_quirks;
 	dev->adapter.dev.parent = dev->dev;
 	dev->adapter.nr = pdev->id;
 	dev->adapter.timeout = AT91_I2C_TIMEOUT;
-- 
2.1.3

[RFC 04/11] i2c: opal: make use of the new infrastructure for quirks

[Wolfram Sang]

Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
---
 drivers/i2c/busses/i2c-opal.c | 22 +++++++++++-----------
 1 file changed, 11 insertions(+), 11 deletions(-)

diff --git a/drivers/i2c/busses/i2c-opal.c b/drivers/i2c/busses/i2c-opal.c
index 16f90b1a7508..f463eae44bf2 100644
--- a/drivers/i2c/busses/i2c-opal.c
+++ b/drivers/i2c/busses/i2c-opal.c
@@ -104,17 +104,6 @@ static int i2c_opal_master_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
 		req.buffer_ra = cpu_to_be64(__pa(msgs[0].buf));
 		break;
 	case 2:
-		/* For two messages, we basically support only simple
-		 * smbus transactions of a write plus a read. We might
-		 * want to allow also two writes but we'd have to bounce
-		 * the data into a single buffer.
-		 */
-		if ((msgs[0].flags & I2C_M_RD) || !(msgs[1].flags & I2C_M_RD))
-			return -EOPNOTSUPP;
-		if (msgs[0].len > 4)
-			return -EOPNOTSUPP;
-		if (msgs[0].addr != msgs[1].addr)
-			return -EOPNOTSUPP;
 		req.type = OPAL_I2C_SM_READ;
 		req.addr = cpu_to_be16(msgs[0].addr);
 		req.subaddr_sz = msgs[0].len;
@@ -210,6 +199,16 @@ static const struct i2c_algorithm i2c_opal_algo = {
 	.functionality	= i2c_opal_func,
 };
 
+/* For two messages, we basically support only simple
+ * smbus transactions of a write plus a read. We might
+ * want to allow also two writes but we'd have to bounce
+ * the data into a single buffer.
+ */
+static struct i2c_adapter_quirks i2c_opal_quirks = {
+	.flags = I2C_ADAPTER_QUIRK_COMB_WRITE_THEN_READ,
+	.max_comb_write_len = 4,
+};
+
 static int i2c_opal_probe(struct platform_device *pdev)
 {
 	struct i2c_adapter	*adapter;
@@ -232,6 +231,7 @@ static int i2c_opal_probe(struct platform_device *pdev)
 
 	adapter->algo = &i2c_opal_algo;
 	adapter->algo_data = (void *)(unsigned long)opal_id;
+	adapter->quirks = &i2c_opal_quirks;
 	adapter->dev.parent = &pdev->dev;
 	adapter->dev.of_node = of_node_get(pdev->dev.of_node);
 	pname = of_get_property(pdev->dev.of_node, "ibm,port-name", NULL);
-- 
2.1.3

[RFC 05/11] i2c: qup: make use of the new infrastructure for quirks

[Wolfram Sang]

Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
---
 drivers/i2c/busses/i2c-qup.c | 21 ++++++++++-----------
 1 file changed, 10 insertions(+), 11 deletions(-)

diff --git a/drivers/i2c/busses/i2c-qup.c b/drivers/i2c/busses/i2c-qup.c
index 4dad23bdffbe..fdcbdab808e9 100644
--- a/drivers/i2c/busses/i2c-qup.c
+++ b/drivers/i2c/busses/i2c-qup.c
@@ -412,17 +412,6 @@ static int qup_i2c_read_one(struct qup_i2c_dev *qup, struct i2c_msg *msg)
 	unsigned long left;
 	int ret;
 
-	/*
-	 * The QUP block will issue a NACK and STOP on the bus when reaching
-	 * the end of the read, the length of the read is specified as one byte
-	 * which limits the possible read to 256 (QUP_READ_LIMIT) bytes.
-	 */
-	if (msg->len > QUP_READ_LIMIT) {
-		dev_err(qup->dev, "HW not capable of reads over %d bytes\n",
-			QUP_READ_LIMIT);
-		return -EINVAL;
-	}
-
 	qup->msg = msg;
 	qup->pos  = 0;
 
@@ -534,6 +523,15 @@ static const struct i2c_algorithm qup_i2c_algo = {
 	.functionality	= qup_i2c_func,
 };
 
+/*
+ * The QUP block will issue a NACK and STOP on the bus when reaching
+ * the end of the read, the length of the read is specified as one byte
+ * which limits the possible read to 256 (QUP_READ_LIMIT) bytes.
+ */
+static struct i2c_adapter_quirks qup_i2c_quirks = {
+	.max_read_len = QUP_READ_LIMIT,
+};
+
 static void qup_i2c_enable_clocks(struct qup_i2c_dev *qup)
 {
 	clk_prepare_enable(qup->clk);
@@ -670,6 +668,7 @@ static int qup_i2c_probe(struct platform_device *pdev)
 
 	i2c_set_adapdata(&qup->adap, qup);
 	qup->adap.algo = &qup_i2c_algo;
+	qup->adap.quirks = &qup_i2c_quirks;
 	qup->adap.dev.parent = qup->dev;
 	qup->adap.dev.of_node = pdev->dev.of_node;
 	strlcpy(qup->adap.name, "QUP I2C adapter", sizeof(qup->adap.name));
-- 
2.1.3

_______________________________________________
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Linuxppc-dev@lists.ozlabs.org
https://lists.ozlabs.org/listinfo/linuxppc-dev

[RFC 06/11] i2c: cpm: make use of the new infrastructure for quirks

[Wolfram Sang]

Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
---
 drivers/i2c/busses/i2c-cpm.c | 20 +++++++++-----------
 1 file changed, 9 insertions(+), 11 deletions(-)

diff --git a/drivers/i2c/busses/i2c-cpm.c b/drivers/i2c/busses/i2c-cpm.c
index 2d466538b2e2..714bdc837769 100644
--- a/drivers/i2c/busses/i2c-cpm.c
+++ b/drivers/i2c/busses/i2c-cpm.c
@@ -308,22 +308,12 @@ static int cpm_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs, int num)
 	struct i2c_reg __iomem *i2c_reg = cpm->i2c_reg;
 	struct i2c_ram __iomem *i2c_ram = cpm->i2c_ram;
 	struct i2c_msg *pmsg;
-	int ret, i;
+	int ret;
 	int tptr;
 	int rptr;
 	cbd_t __iomem *tbdf;
 	cbd_t __iomem *rbdf;
 
-	if (num > CPM_MAXBD)
-		return -EINVAL;
-
-	/* Check if we have any oversized READ requests */
-	for (i = 0; i < num; i++) {
-		pmsg = &msgs[i];
-		if (pmsg->len >= CPM_MAX_READ)
-			return -EINVAL;
-	}
-
 	/* Reset to use first buffer */
 	out_be16(&i2c_ram->rbptr, in_be16(&i2c_ram->rbase));
 	out_be16(&i2c_ram->tbptr, in_be16(&i2c_ram->tbase));
@@ -424,10 +414,18 @@ static const struct i2c_algorithm cpm_i2c_algo = {
 	.functionality = cpm_i2c_func,
 };
 
+/* CPM_MAX_READ is also limiting writes according to the code! */
+static struct i2c_adapter_quirks cpm_i2c_quirks = {
+	.max_num_msgs = CPM_MAXBD,
+	.max_read_len = CPM_MAX_READ,
+	.max_write_len = CPM_MAX_READ,
+};
+
 static const struct i2c_adapter cpm_ops = {
 	.owner		= THIS_MODULE,
 	.name		= "i2c-cpm",
 	.algo		= &cpm_i2c_algo,
+	.quirks		= &cpm_i2c_quirks,
 };
 
 static int cpm_i2c_setup(struct cpm_i2c *cpm)
-- 
2.1.3

[RFC 07/11] i2c: axxia: make use of the new infrastructure for quirks

[Wolfram Sang]

Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
---
 drivers/i2c/busses/i2c-axxia.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/drivers/i2c/busses/i2c-axxia.c b/drivers/i2c/busses/i2c-axxia.c
index 768a598d8d03..488c5d3bf9db 100644
--- a/drivers/i2c/busses/i2c-axxia.c
+++ b/drivers/i2c/busses/i2c-axxia.c
@@ -336,11 +336,6 @@ static int axxia_i2c_xfer_msg(struct axxia_i2c_dev *idev, struct i2c_msg *msg)
 	u32 addr_1, addr_2;
 	int ret;
 
-	if (msg->len > 255) {
-		dev_warn(idev->dev, "unsupported length %u\n", msg->len);
-		return -EINVAL;
-	}
-
 	idev->msg = msg;
 	idev->msg_xfrd = 0;
 	idev->msg_err = 0;
@@ -454,6 +449,11 @@ static const struct i2c_algorithm axxia_i2c_algo = {
 	.functionality = axxia_i2c_func,
 };
 
+static struct i2c_adapter_quirks axxia_i2c_quirks = {
+	.max_read_len = 255,
+	.max_write_len = 255,
+};
+
 static int axxia_i2c_probe(struct platform_device *pdev)
 {
 	struct device_node *np = pdev->dev.of_node;
@@ -511,6 +511,7 @@ static int axxia_i2c_probe(struct platform_device *pdev)
 	strlcpy(idev->adapter.name, pdev->name, sizeof(idev->adapter.name));
 	idev->adapter.owner = THIS_MODULE;
 	idev->adapter.algo = &axxia_i2c_algo;
+	idev->adapter.quirks = &axxia_i2c_quirks;
 	idev->adapter.dev.parent = &pdev->dev;
 	idev->adapter.dev.of_node = pdev->dev.of_node;
 
-- 
2.1.3

[RFC 08/11] i2c: dln2: make use of the new infrastructure for quirks

[Wolfram Sang]

Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
---
 drivers/i2c/busses/i2c-dln2.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/drivers/i2c/busses/i2c-dln2.c b/drivers/i2c/busses/i2c-dln2.c
index b3fb86af4cbb..b6f9ba7eb175 100644
--- a/drivers/i2c/busses/i2c-dln2.c
+++ b/drivers/i2c/busses/i2c-dln2.c
@@ -144,7 +144,6 @@ static int dln2_i2c_xfer(struct i2c_adapter *adapter,
 {
 	struct dln2_i2c *dln2 = i2c_get_adapdata(adapter);
 	struct i2c_msg *pmsg;
-	struct device *dev = &dln2->adapter.dev;
 	int i;
 
 	for (i = 0; i < num; i++) {
@@ -152,11 +151,6 @@ static int dln2_i2c_xfer(struct i2c_adapter *adapter,
 
 		pmsg = &msgs[i];
 
-		if (pmsg->len > DLN2_I2C_MAX_XFER_SIZE) {
-			dev_warn(dev, "maximum transfer size exceeded\n");
-			return -EOPNOTSUPP;
-		}
-
 		if (pmsg->flags & I2C_M_RD) {
 			ret = dln2_i2c_read(dln2, pmsg->addr, pmsg->buf,
 					    pmsg->len);
@@ -187,6 +181,11 @@ static const struct i2c_algorithm dln2_i2c_usb_algorithm = {
 	.functionality = dln2_i2c_func,
 };
 
+static struct i2c_adapter_quirks dln2_i2c_quirks = {
+	.max_read_len = DLN2_I2C_MAX_XFER_SIZE,
+	.max_write_len = DLN2_I2C_MAX_XFER_SIZE,
+};
+
 static int dln2_i2c_probe(struct platform_device *pdev)
 {
 	int ret;
@@ -209,6 +208,7 @@ static int dln2_i2c_probe(struct platform_device *pdev)
 	dln2->adapter.owner = THIS_MODULE;
 	dln2->adapter.class = I2C_CLASS_HWMON;
 	dln2->adapter.algo = &dln2_i2c_usb_algorithm;
+	dln2->adapter.quirks = &dln2_i2c_quirks;
 	dln2->adapter.dev.parent = dev;
 	i2c_set_adapdata(&dln2->adapter, dln2);
 	snprintf(dln2->adapter.name, sizeof(dln2->adapter.name), "%s-%s-%d",
-- 
2.1.3

[RFC 09/11] i2c: powermac: make use of the new infrastructure for quirks

[Wolfram Sang]

Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
---
 drivers/i2c/busses/i2c-powermac.c | 10 ++++------
 1 file changed, 4 insertions(+), 6 deletions(-)

diff --git a/drivers/i2c/busses/i2c-powermac.c b/drivers/i2c/busses/i2c-powermac.c
index 60a53c169ed2..6abcf696e359 100644
--- a/drivers/i2c/busses/i2c-powermac.c
+++ b/drivers/i2c/busses/i2c-powermac.c
@@ -153,12 +153,6 @@ static int i2c_powermac_master_xfer(	struct i2c_adapter *adap,
 	int			read;
 	int			addrdir;
 
-	if (num != 1) {
-		dev_err(&adap->dev,
-			"Multi-message I2C transactions not supported\n");
-		return -EOPNOTSUPP;
-	}
-
 	if (msgs->flags & I2C_M_TEN)
 		return -EINVAL;
 	read = (msgs->flags & I2C_M_RD) != 0;
@@ -205,6 +199,9 @@ static const struct i2c_algorithm i2c_powermac_algorithm = {
 	.functionality	= i2c_powermac_func,
 };
 
+static struct i2c_adapter_quirks i2c_powermac_quirks = {
+	.max_num_msgs = 1,
+};
 
 static int i2c_powermac_remove(struct platform_device *dev)
 {
@@ -434,6 +431,7 @@ static int i2c_powermac_probe(struct platform_device *dev)
 
 	platform_set_drvdata(dev, adapter);
 	adapter->algo = &i2c_powermac_algorithm;
+	adapter->quirks = &i2c_powermac_quirks;
 	i2c_set_adapdata(adapter, bus);
 	adapter->dev.parent = &dev->dev;
 
-- 
2.1.3

[RFC 10/11] i2c: viperboard: make use of the new infrastructure for quirks

[Wolfram Sang]

Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
---
 drivers/i2c/busses/i2c-viperboard.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/drivers/i2c/busses/i2c-viperboard.c b/drivers/i2c/busses/i2c-viperboard.c
index 7533fa34d737..47e88adf2011 100644
--- a/drivers/i2c/busses/i2c-viperboard.c
+++ b/drivers/i2c/busses/i2c-viperboard.c
@@ -288,10 +288,6 @@ static int vprbrd_i2c_xfer(struct i2c_adapter *i2c, struct i2c_msg *msgs,
 			i, pmsg->flags & I2C_M_RD ? "read" : "write",
 			pmsg->flags, pmsg->len, pmsg->addr);
 
-		/* msgs longer than 2048 bytes are not supported by adapter */
-		if (pmsg->len > 2048)
-			return -EINVAL;
-
 		mutex_lock(&vb->lock);
 		/* directly send the message */
 		if (pmsg->flags & I2C_M_RD) {
@@ -358,6 +354,11 @@ static const struct i2c_algorithm vprbrd_algorithm = {
 	.functionality	= vprbrd_i2c_func,
 };
 
+static struct i2c_adapter_quirks vprbrd_quirks = {
+	.max_read_len = 2048,
+	.max_write_len = 2048,
+};
+
 static int vprbrd_i2c_probe(struct platform_device *pdev)
 {
 	struct vprbrd *vb = dev_get_drvdata(pdev->dev.parent);
@@ -373,6 +374,7 @@ static int vprbrd_i2c_probe(struct platform_device *pdev)
 	vb_i2c->i2c.owner = THIS_MODULE;
 	vb_i2c->i2c.class = I2C_CLASS_HWMON;
 	vb_i2c->i2c.algo = &vprbrd_algorithm;
+	vb_i2c->i2c.quirks = &vprbrd_quirks;
 	vb_i2c->i2c.algo_data = vb;
 	/* save the param in usb capabable memory */
 	vb_i2c->bus_freq_param = i2c_bus_param;
-- 
2.1.3

[RFC 11/11] i2c: pmcmsp: make use of the new infrastructure for quirks

[Wolfram Sang]

Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
---
 drivers/i2c/busses/i2c-pmcmsp.c | 42 ++++++++++++++++-------------------------
 1 file changed, 16 insertions(+), 26 deletions(-)

diff --git a/drivers/i2c/busses/i2c-pmcmsp.c b/drivers/i2c/busses/i2c-pmcmsp.c
index 44f03eed00dd..e06efee9fa70 100644
--- a/drivers/i2c/busses/i2c-pmcmsp.c
+++ b/drivers/i2c/busses/i2c-pmcmsp.c
@@ -463,14 +463,6 @@ static enum pmcmsptwi_xfer_result pmcmsptwi_xfer_cmd(
 		return -EINVAL;
 	}
 
-	if (cmd->read_len > MSP_MAX_BYTES_PER_RW ||
-	    cmd->write_len > MSP_MAX_BYTES_PER_RW) {
-		dev_err(&pmcmsptwi_adapter.dev,
-			"%s: Cannot transfer more than %d bytes\n",
-			__func__, MSP_MAX_BYTES_PER_RW);
-		return -EINVAL;
-	}
-
 	mutex_lock(&data->lock);
 	dev_dbg(&pmcmsptwi_adapter.dev,
 		"Setting address to 0x%04x\n", cmd->addr);
@@ -527,25 +519,14 @@ static int pmcmsptwi_master_xfer(struct i2c_adapter *adap,
 	struct pmcmsptwi_cfg oldcfg, newcfg;
 	int ret;
 
-	if (num > 2) {
-		dev_dbg(&adap->dev, "%d messages unsupported\n", num);
-		return -EINVAL;
-	} else if (num == 2) {
-		/* Check for a dual write-then-read command */
+	if (num == 2) {
 		struct i2c_msg *nextmsg = msg + 1;
-		if (!(msg->flags & I2C_M_RD) &&
-		    (nextmsg->flags & I2C_M_RD) &&
-		    msg->addr == nextmsg->addr) {
-			cmd.type = MSP_TWI_CMD_WRITE_READ;
-			cmd.write_len = msg->len;
-			cmd.write_data = msg->buf;
-			cmd.read_len = nextmsg->len;
-			cmd.read_data = nextmsg->buf;
-		} else {
-			dev_dbg(&adap->dev,
-				"Non write-read dual messages unsupported\n");
-			return -EINVAL;
-		}
+
+		cmd.type = MSP_TWI_CMD_WRITE_READ;
+		cmd.write_len = msg->len;
+		cmd.write_data = msg->buf;
+		cmd.read_len = nextmsg->len;
+		cmd.read_data = nextmsg->buf;
 	} else if (msg->flags & I2C_M_RD) {
 		cmd.type = MSP_TWI_CMD_READ;
 		cmd.read_len = msg->len;
@@ -605,6 +586,14 @@ static u32 pmcmsptwi_i2c_func(struct i2c_adapter *adapter)
 		I2C_FUNC_SMBUS_WORD_DATA | I2C_FUNC_SMBUS_PROC_CALL;
 }
 
+static struct i2c_adapter_quirks pmcmsptwi_i2c_quirks = {
+	.flags = I2C_ADAPTER_QUIRK_COMB_WRITE_THEN_READ,
+	.max_write_len = MSP_MAX_BYTES_PER_RW,
+	.max_read_len = MSP_MAX_BYTES_PER_RW,
+	.max_comb_write_len = MSP_MAX_BYTES_PER_RW,
+	.max_comb_read_len = MSP_MAX_BYTES_PER_RW,
+};
+
 /* -- Initialization -- */
 
 static struct i2c_algorithm pmcmsptwi_algo = {
@@ -616,6 +605,7 @@ static struct i2c_adapter pmcmsptwi_adapter = {
 	.owner		= THIS_MODULE,
 	.class		= I2C_CLASS_HWMON | I2C_CLASS_SPD,
 	.algo		= &pmcmsptwi_algo,
+	.quirks		= &pmcmsptwi_i2c_quirks,
 	.name		= DRV_NAME,
 };
 
-- 
2.1.3