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Date: Sat, 28 May 2011 20:52:29 +0100
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From: Stefan Hajnoczi <stefanha@gmail.com>
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Subject: Re: [Qemu-devel] [Qemu-trivial] [PATCH] bitbang_i2c: Fix spurious
	slave read after NACK
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To: Andrzej Zaborowski <balrog@zabor.org>
Cc: qemu-trivial@nongnu.org, qemu-devel@nongnu.org, Marcus Comstedt <marcus@mc.pp.se>

On Sat, May 28, 2011 at 3:55 PM, Marcus Comstedt <marcus@mc.pp.se> wrote:
> After NACKing a read operation, a raising SCL should not trigger a new
> read from the slave. =A0Introduce a new state which just waits for a stop
> or start condition after NACK.
>
> Signed-off-by: Marcus Comstedt <marcus@mc.pp.se>
> ---
> =A0hw/bitbang_i2c.c | =A0 =A05 ++++-
> =A01 files changed, 4 insertions(+), 1 deletions(-)

Seems like a simple change but I'm not familiar with the code or I2C
details.  Andrzej, care to take a look?

> diff --git a/hw/bitbang_i2c.c b/hw/bitbang_i2c.c
> index 4ee99a1..2937b5c 100644
> --- a/hw/bitbang_i2c.c
> +++ b/hw/bitbang_i2c.c
> @@ -38,7 +38,8 @@ typedef enum bitbang_i2c_state {
> =A0 =A0 RECEIVING_BIT2,
> =A0 =A0 RECEIVING_BIT1,
> =A0 =A0 RECEIVING_BIT0,
> - =A0 =A0SENDING_ACK
> + =A0 =A0SENDING_ACK,
> + =A0 =A0SENT_NACK
> =A0} bitbang_i2c_state;
>
> =A0struct bitbang_i2c_interface {
> @@ -115,6 +116,7 @@ int bitbang_i2c_set(bitbang_i2c_interface *i2c, int l=
ine, int level)
> =A0 =A0 }
> =A0 =A0 switch (i2c->state) {
> =A0 =A0 case STOPPED:
> + =A0 =A0case SENT_NACK:
> =A0 =A0 =A0 =A0 return bitbang_i2c_ret(i2c, 1);
>
> =A0 =A0 case SENDING_BIT7 ... SENDING_BIT0:
> @@ -155,6 +157,7 @@ int bitbang_i2c_set(bitbang_i2c_interface *i2c, int l=
ine, int level)
> =A0 =A0 =A0 =A0 i2c->state =3D RECEIVING_BIT7;
> =A0 =A0 =A0 =A0 if (data !=3D 0) {
> =A0 =A0 =A0 =A0 =A0 =A0 DPRINTF("NACKED\n");
> + =A0 =A0 =A0 =A0 =A0 =A0i2c->state =3D SENT_NACK;
> =A0 =A0 =A0 =A0 =A0 =A0 i2c_nack(i2c->bus);
> =A0 =A0 =A0 =A0 } else {
> =A0 =A0 =A0 =A0 =A0 =A0 DPRINTF("ACKED\n");
> --
> 1.7.4.1
>
>
>