Hi Jean,
I have already discussed your questions with you in attached email. See
bellow. The twi controller is designed to support SMBus protocol in
hardware. That's why we implement bfin_twi_smbus_xfer().
Sonic
=====================================
from Jean Delvare <[EMAIL PROTECTED]>
to Sonic Zhang <[EMAIL PROTECTED]>,
date Wed, Nov 14, 2007 at 9:20 PM
subject Re: [PATCH 1/4] Blackfin I2C/TWI driver: Add repeat start
feature to avoid break of a bundle of i2c master xfer operation.
hide details 11/14/07
Reply
Hi Sonic,
- Hide quoted text -
On Thu, 8 Nov 2007 13:14:56 +0800, Sonic Zhang wrote:
> TWI_I2C_MODE_REPEAT:
> static int bfin_twi_master_xfer(struct i2c_adapter *adap, struct
> i2c_msg *msgs, int num);
>
> From transaction 1 to N do simple read or write
> {
> start,
> read or write,
> address,
> data,
> if Not N
> { restart }
> else
> { stop }
> }
>
> TWI_I2C_MODE_COMBINED:
> static int bfin_twi_master_xfer(struct i2c_adapter *adap, struct
> i2c_msg *msgs, int num);
>
> Write then read transactions in SMBus
> {
> start,
> write,
> address,
> data,
> restart,
> read,
> address,
> data,
> stop.
> - Hide quoted text -
> }
>
OK, thanks for the clarification. The above looks OK to me, if that's
what the driver implements then there's no problem. However, please
realize that TWI_I2C_MODE_COMBINED is a subset of TWI_I2C_MODE_REPEAT
(with N = 2, first message is a write and second message is a read.)
This means that TWI_I2C_MODE_COMBINED is not strictly needed and could
be implemented using TWI_I2C_MODE_REPEAT. As a matter of fact most I2C
master drivers in Linux do that, i.e. they implement .master_xfer and
not .smbus_xfer. i2c-core can emulate .smbus_xfer from .master_xfer.
I don't know the i2c-bfin-twi driver in details so there might be a
reason why you implemented both methods that I don't understand, but
from my point of view, you should be able to delete
bfin_twi_smbus_xfer() and your driver would still work the exact same
as it does today. The advantage would be a smaller driver, so a lower
risk to have hidden bugs.
Thanks,
--
Jean Delvare
Reply
Forward
Sonic Zhang to Jean
show details 11/15/07
Reply
from Sonic Zhang <[EMAIL PROTECTED]>
to Jean Delvare <[EMAIL PROTECTED]>,
date Thu, Nov 15, 2007 at 10:50 AM
subject Re: [PATCH 1/4] Blackfin I2C/TWI driver: Add repeat start
feature to avoid break of a bundle of i2c master xfer operation.
mailed-by gmail.com
hide details 11/15/07
Reply
Thank you for your great advises.
Sonic
-----Original Message-----
From: Jean Delvare [mailto:[EMAIL PROTECTED]
Sent: Tuesday, March 25, 2008 2:21 AM
To: Bryan Wu
Cc: [email protected]; Sonic Zhang
Subject: Re: [PATCH 1/6] Blackfin I2C/TWI driver: Add repeat start
feature to avoid break of a bundle of i2c master xfer operation.
Hi Bryan,
On Fri, 14 Mar 2008 00:22:35 -0700, Bryan Wu wrote:
> From: Sonic Zhang <[EMAIL PROTECTED]>
>
> - Create a new mode TWI_I2C_MODE_REPEAT.
> - No change to smbus operation.
>
> Signed-off-by: Sonic Zhang <[EMAIL PROTECTED]>
> Signed-off-by: Bryan Wu <[EMAIL PROTECTED]>
> Signed-off-by: Bryan Wu <[EMAIL PROTECTED]>
Just one Signed-off-by per person, please.
> ---
> drivers/i2c/busses/i2c-bfin-twi.c | 183
> +++++++++++++++++++++++--------------
> 1 files changed, 113 insertions(+), 70 deletions(-)
>
> diff --git a/drivers/i2c/busses/i2c-bfin-twi.c
> b/drivers/i2c/busses/i2c-bfin-twi.c
> index 7dbdaeb..ea15125 100644
> --- a/drivers/i2c/busses/i2c-bfin-twi.c
> +++ b/drivers/i2c/busses/i2c-bfin-twi.c
> (...)
It seems that this patch is the exact same as the one you posted back in
November 2007:
http://lists.lm-sensors.org/pipermail/i2c/2007-November/002119.html
I did review this patch:
http://lists.lm-sensors.org/pipermail/i2c/2007-November/002121.html
So I would appreciate if you could take my comments into account and
post an updated version.
Thanks,
--
Jean Delvare
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