From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jean Delvare Subject: Re: [PATCH] i2c-dev: Add support for I2C_M_RECV_LEN Date: Fri, 6 Apr 2012 08:37:51 +0200 Message-ID: <20120406083751.46fd23c5@endymion.delvare> References: <20120315180835.2e669111@endymion.delvare> <20120331081927.2438ea9e@endymion.delvare> <4F7CD11C.2090801@interlog.com> <20120405092422.453edecf@endymion.delvare> <4F7E3267.9040306@interlog.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <4F7E3267.9040306-qazKcTl6WRFWk0Htik3J/w@public.gmane.org> Sender: linux-i2c-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: dgilbert-qazKcTl6WRFWk0Htik3J/w@public.gmane.org Cc: Linux I2C List-Id: linux-i2c@vger.kernel.org On Thu, 05 Apr 2012 20:01:43 -0400, Douglas Gilbert wrote: > On 12-04-05 03:24 AM, Jean Delvare wrote: > > As the bus driver side implementation of I2C_M_RECV_LEN is heavily > > tied to SMBus, we can't support received length over 32 bytes, but > > let's at least support that. > > > > In practice, the caller will have to setup a buffer large enough to > > cover the case where received length byte has value 32, so minimum > > 32 + 1 = 33 bytes, possibly more if there is a fixed number of bytes > > added for the specific slave (for example a checksum.) > > Either I am misunderstanding how to use this new patch or it is > broken. After replacing the original patch with this one, setting > msg->buf[0] to 2, my test program only sees the first two bytes > of expected data: > 08 81 > That is down from 8 bytes from the previous patch and 10 bytes > expected from the SM130. Does your I2C bus driver process I2C_M_RECV_LEN at all? I bet not. You'll have to fix that. It's fairly easy, see the reference implementation in i2c-algo-bit.c:readbytes(). The completely untested attempt below may do, if not you'll have to fix my code: --- drivers/i2c/busses/i2c-at91.c | 17 ++++++++++++----- 1 file changed, 12 insertions(+), 5 deletions(-) --- linux-3.4-rc1.orig/drivers/i2c/busses/i2c-at91.c 2012-04-06 08:27:38.000000000 +0200 +++ linux-3.4-rc1/drivers/i2c/busses/i2c-at91.c 2012-04-06 08:36:47.379360574 +0200 @@ -159,13 +159,14 @@ static short at91_poll_status(unsigned l return (loop_cntr > 0); } -static int xfer_read(struct i2c_adapter *adap, unsigned char *buf, int length) +static int xfer_read(struct i2c_adapter *adap, unsigned char *buf, int length, + int recv_len) { int nack_seen = 0; int sent_stop = 0; /* Send Start */ - if (1 == length) { + if ((1 == length) && !recv_len) { at91_twi_write(AT91_TWI_CR, AT91_TWI_START | AT91_TWI_STOP); sent_stop = 1; } else @@ -174,7 +175,7 @@ static int xfer_read(struct i2c_adapter /* Read data */ while (length--) { /* send Stop before reading last byte (if not already done) */ - if ((0 == length) && (0 == sent_stop)) + if ((0 == length) && (0 == sent_stop) && !recv_len) at91_twi_write(AT91_TWI_CR, AT91_TWI_STOP); if (!at91_poll_status(AT91_TWI_RXRDY, &nack_seen)) { dev_dbg(&adap->dev, "RXRDY timeout\n"); @@ -184,7 +185,12 @@ static int xfer_read(struct i2c_adapter /* NACK supplies Stop */ return -EREMOTEIO; } - *buf++ = (at91_twi_read(AT91_TWI_RHR) & 0xff); + *buf = (at91_twi_read(AT91_TWI_RHR) & 0xff); + if (recv_len) { + length += *buf; + recv_len = 0; + } + buf++; } return 0; @@ -257,7 +263,8 @@ static int at91_xfer(struct i2c_adapter if (pmsg->len && pmsg->buf) { /* sanity check */ if (pmsg->flags & I2C_M_RD) - ret = xfer_read(adap, pmsg->buf, pmsg->len); + ret = xfer_read(adap, pmsg->buf, pmsg->len, + pmsg->flags & I2C_M_RECV_LEN); else ret = xfer_write(adap, pmsg->buf, pmsg->len); -- Jean Delvare