[deliverable/linux.git] / net / nfc / nci / spi.c

/*
 * Copyright (C) 2013  Intel Corporation. All rights reserved.
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms and conditions of the GNU General Public License,
 * version 2, as published by the Free Software Foundation.
 *
 * This program is distributed in the hope it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
 * more details.
 *
 * You should have received a copy of the GNU General Public License along with
 * this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin St - Fifth Floor, Boston, MA 02110-1301 USA.
 *
 */

#define pr_fmt(fmt) "nci_spi: %s: " fmt, __func__

#include <linux/module.h>

#include <linux/export.h>
#include <linux/spi/spi.h>
#include <linux/crc-ccitt.h>
#include <net/nfc/nci_core.h>

#define NCI_SPI_ACK_SHIFT		6
#define NCI_SPI_MSB_PAYLOAD_MASK	0x3F

#define NCI_SPI_SEND_TIMEOUT	(NCI_CMD_TIMEOUT > NCI_DATA_TIMEOUT ? \
					NCI_CMD_TIMEOUT : NCI_DATA_TIMEOUT)

#define NCI_SPI_DIRECT_WRITE	0x01
#define NCI_SPI_DIRECT_READ	0x02

#define ACKNOWLEDGE_NONE	0
#define ACKNOWLEDGE_ACK		1
#define ACKNOWLEDGE_NACK	2

#define CRC_INIT		0xFFFF

static int __nci_spi_send(struct nci_spi *nspi, struct sk_buff *skb,
			  int cs_change)
{
	struct spi_message m;
	struct spi_transfer t;

	memset(&t, 0, sizeof(struct spi_transfer));
	/* a NULL skb means we just want the SPI chip select line to raise */
	if (skb) {
		t.tx_buf = skb->data;
		t.len = skb->len;
	} else {
		/* still set tx_buf non NULL to make the driver happy */
		t.tx_buf = &t;
		t.len = 0;
	}
	t.cs_change = cs_change;
	t.delay_usecs = nspi->xfer_udelay;
	t.speed_hz = nspi->xfer_speed_hz;

	spi_message_init(&m);
	spi_message_add_tail(&t, &m);

	return spi_sync(nspi->spi, &m);
}

int nci_spi_send(struct nci_spi *nspi,
		 struct completion *write_handshake_completion,
		 struct sk_buff *skb)
{
	unsigned int payload_len = skb->len;
	unsigned char *hdr;
	int ret;
	long completion_rc;

	/* add the NCI SPI header to the start of the buffer */
	hdr = skb_push(skb, NCI_SPI_HDR_LEN);
	hdr[0] = NCI_SPI_DIRECT_WRITE;
	hdr[1] = nspi->acknowledge_mode;
	hdr[2] = payload_len >> 8;
	hdr[3] = payload_len & 0xFF;

	if (nspi->acknowledge_mode == NCI_SPI_CRC_ENABLED) {
		u16 crc;

		crc = crc_ccitt(CRC_INIT, skb->data, skb->len);
		*skb_put(skb, 1) = crc >> 8;
		*skb_put(skb, 1) = crc & 0xFF;
	}

	if (write_handshake_completion)	{
		/* Trick SPI driver to raise chip select */
		ret = __nci_spi_send(nspi, NULL, 1);
		if (ret)
			goto done;

		/* wait for NFC chip hardware handshake to complete */
		if (wait_for_completion_timeout(write_handshake_completion,
						msecs_to_jiffies(1000)) == 0) {
			ret = -ETIME;
			goto done;
		}
	}

	ret = __nci_spi_send(nspi, skb, 0);
	if (ret != 0 || nspi->acknowledge_mode == NCI_SPI_CRC_DISABLED)
		goto done;

	reinit_completion(&nspi->req_completion);
	completion_rc =	wait_for_completion_interruptible_timeout(
							&nspi->req_completion,
							NCI_SPI_SEND_TIMEOUT);

	if (completion_rc <= 0 || nspi->req_result == ACKNOWLEDGE_NACK)
		ret = -EIO;

done:
	kfree_skb(skb);

	return ret;
}
EXPORT_SYMBOL_GPL(nci_spi_send);

/* ---- Interface to NCI SPI drivers ---- */

/**
 * nci_spi_allocate_spi - allocate a new nci spi
 *
 * @spi: SPI device
 * @acknowledge_mode: Acknowledge mode used by the NFC device
 * @delay: delay between transactions in us
 * @ndev: nci dev to send incoming nci frames to
 */
struct nci_spi *nci_spi_allocate_spi(struct spi_device *spi,
				     u8 acknowledge_mode, unsigned int delay,
				     struct nci_dev *ndev)
{
	struct nci_spi *nspi;

	nspi = devm_kzalloc(&spi->dev, sizeof(struct nci_spi), GFP_KERNEL);
	if (!nspi)
		return NULL;

	nspi->acknowledge_mode = acknowledge_mode;
	nspi->xfer_udelay = delay;
	/* Use controller max SPI speed by default */
	nspi->xfer_speed_hz = 0;
	nspi->spi = spi;
	nspi->ndev = ndev;
	init_completion(&nspi->req_completion);

	return nspi;
}
EXPORT_SYMBOL_GPL(nci_spi_allocate_spi);

static int send_acknowledge(struct nci_spi *nspi, u8 acknowledge)
{
	struct sk_buff *skb;
	unsigned char *hdr;
	u16 crc;
	int ret;

	skb = nci_skb_alloc(nspi->ndev, 0, GFP_KERNEL);

	/* add the NCI SPI header to the start of the buffer */
	hdr = skb_push(skb, NCI_SPI_HDR_LEN);
	hdr[0] = NCI_SPI_DIRECT_WRITE;
	hdr[1] = NCI_SPI_CRC_ENABLED;
	hdr[2] = acknowledge << NCI_SPI_ACK_SHIFT;
	hdr[3] = 0;

	crc = crc_ccitt(CRC_INIT, skb->data, skb->len);
	*skb_put(skb, 1) = crc >> 8;
	*skb_put(skb, 1) = crc & 0xFF;

	ret = __nci_spi_send(nspi, skb, 0);

	kfree_skb(skb);

	return ret;
}

static struct sk_buff *__nci_spi_read(struct nci_spi *nspi)
{
	struct sk_buff *skb;
	struct spi_message m;
	unsigned char req[2], resp_hdr[2];
	struct spi_transfer tx, rx;
	unsigned short rx_len = 0;
	int ret;

	spi_message_init(&m);

	memset(&tx, 0, sizeof(struct spi_transfer));
	req[0] = NCI_SPI_DIRECT_READ;
	req[1] = nspi->acknowledge_mode;
	tx.tx_buf = req;
	tx.len = 2;
	tx.cs_change = 0;
	tx.speed_hz = nspi->xfer_speed_hz;
	spi_message_add_tail(&tx, &m);

	memset(&rx, 0, sizeof(struct spi_transfer));
	rx.rx_buf = resp_hdr;
	rx.len = 2;
	rx.cs_change = 1;
	rx.speed_hz = nspi->xfer_speed_hz;
	spi_message_add_tail(&rx, &m);

	ret = spi_sync(nspi->spi, &m);
	if (ret)
		return NULL;

	if (nspi->acknowledge_mode == NCI_SPI_CRC_ENABLED)
		rx_len = ((resp_hdr[0] & NCI_SPI_MSB_PAYLOAD_MASK) << 8) +
				resp_hdr[1] + NCI_SPI_CRC_LEN;
	else
		rx_len = (resp_hdr[0] << 8) | resp_hdr[1];

	skb = nci_skb_alloc(nspi->ndev, rx_len, GFP_KERNEL);
	if (!skb)
		return NULL;

	spi_message_init(&m);

	memset(&rx, 0, sizeof(struct spi_transfer));
	rx.rx_buf = skb_put(skb, rx_len);
	rx.len = rx_len;
	rx.cs_change = 0;
	rx.delay_usecs = nspi->xfer_udelay;
	rx.speed_hz = nspi->xfer_speed_hz;
	spi_message_add_tail(&rx, &m);

	ret = spi_sync(nspi->spi, &m);
	if (ret)
		goto receive_error;

	if (nspi->acknowledge_mode == NCI_SPI_CRC_ENABLED) {
		*skb_push(skb, 1) = resp_hdr[1];
		*skb_push(skb, 1) = resp_hdr[0];
	}

	return skb;

receive_error:
	kfree_skb(skb);

	return NULL;
}

static int nci_spi_check_crc(struct sk_buff *skb)
{
	u16 crc_data = (skb->data[skb->len - 2] << 8) |
			skb->data[skb->len - 1];
	int ret;

	ret = (crc_ccitt(CRC_INIT, skb->data, skb->len - NCI_SPI_CRC_LEN)
			== crc_data);

	skb_trim(skb, skb->len - NCI_SPI_CRC_LEN);

	return ret;
}

static u8 nci_spi_get_ack(struct sk_buff *skb)
{
	u8 ret;

	ret = skb->data[0] >> NCI_SPI_ACK_SHIFT;

	/* Remove NFCC part of the header: ACK, NACK and MSB payload len */
	skb_pull(skb, 2);

	return ret;
}

/**
 * nci_spi_read - read frame from NCI SPI drivers
 *
 * @nspi: The nci spi
 * Context: can sleep
 *
 * This call may only be used from a context that may sleep.  The sleep
 * is non-interruptible, and has no timeout.
 *
 * It returns an allocated skb containing the frame on success, or NULL.
 */
struct sk_buff *nci_spi_read(struct nci_spi *nspi)
{
	struct sk_buff *skb;

	/* Retrieve frame from SPI */
	skb = __nci_spi_read(nspi);
	if (!skb)
		goto done;

	if (nspi->acknowledge_mode == NCI_SPI_CRC_ENABLED) {
		if (!nci_spi_check_crc(skb)) {
			send_acknowledge(nspi, ACKNOWLEDGE_NACK);
			goto done;
		}

		/* In case of acknowledged mode: if ACK or NACK received,
		 * unblock completion of latest frame sent.
		 */
		nspi->req_result = nci_spi_get_ack(skb);
		if (nspi->req_result)
			complete(&nspi->req_completion);
	}

	/* If there is no payload (ACK/NACK only frame),
	 * free the socket buffer
	 */
	if (!skb->len) {
		kfree_skb(skb);
		skb = NULL;
		goto done;
	}

	if (nspi->acknowledge_mode == NCI_SPI_CRC_ENABLED)
		send_acknowledge(nspi, ACKNOWLEDGE_ACK);

done:

	return skb;
}
EXPORT_SYMBOL_GPL(nci_spi_read);

MODULE_LICENSE("GPL");
Commit	Line	Data
8a00a61b FD	1	/*
	2	* Copyright (C) 2013 Intel Corporation. All rights reserved.
	3	*
	4	* This program is free software; you can redistribute it and/or modify it
	5	* under the terms and conditions of the GNU General Public License,
	6	* version 2, as published by the Free Software Foundation.
	7	*
	8	* This program is distributed in the hope it will be useful, but WITHOUT
	9	* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
	10	* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
	11	* more details.
	12	*
	13	* You should have received a copy of the GNU General Public License along with
	14	* this program; if not, write to the Free Software Foundation, Inc.,
	15	* 51 Franklin St - Fifth Floor, Boston, MA 02110-1301 USA.
	16	*
	17	*/
	18
	19	#define pr_fmt(fmt) "nci_spi: %s: " fmt, __func__
	20
fcd9d046 VC	21	#include <linux/module.h>
fcd9d046 VC	22
8a00a61b FD	23	#include <linux/export.h>
8a00a61b FD	24	#include <linux/spi/spi.h>
ee9596d4	25	#include <linux/crc-ccitt.h>
8a00a61b FD	26	#include <net/nfc/nci_core.h>
8a00a61b FD	27
391d8a2d FD	28	#define NCI_SPI_ACK_SHIFT 6
391d8a2d FD	29	#define NCI_SPI_MSB_PAYLOAD_MASK 0x3F
8a00a61b	30
ee9596d4 FD	31	#define NCI_SPI_SEND_TIMEOUT (NCI_CMD_TIMEOUT > NCI_DATA_TIMEOUT ? \
	32	NCI_CMD_TIMEOUT : NCI_DATA_TIMEOUT)
	33
	34	#define NCI_SPI_DIRECT_WRITE 0x01
	35	#define NCI_SPI_DIRECT_READ 0x02
	36
	37	#define ACKNOWLEDGE_NONE 0
	38	#define ACKNOWLEDGE_ACK 1
	39	#define ACKNOWLEDGE_NACK 2
	40
	41	#define CRC_INIT 0xFFFF
	42
2bed2785 EL	43	static int __nci_spi_send(struct nci_spi nspi, struct sk_buff skb,
2bed2785 EL	44	int cs_change)
ee9596d4 FD	45	{
	46	struct spi_message m;
	47	struct spi_transfer t;
	48
a4ada6ca	49	memset(&t, 0, sizeof(struct spi_transfer));
2bed2785 EL	50	/* a NULL skb means we just want the SPI chip select line to raise */
	51	if (skb) {
	52	t.tx_buf = skb->data;
	53	t.len = skb->len;
	54	} else {
	55	/* still set tx_buf non NULL to make the driver happy */
	56	t.tx_buf = &t;
	57	t.len = 0;
	58	}
	59	t.cs_change = cs_change;
fa544fff	60	t.delay_usecs = nspi->xfer_udelay;
2bd83245	61	t.speed_hz = nspi->xfer_speed_hz;
ee9596d4 FD	62
	63	spi_message_init(&m);
	64	spi_message_add_tail(&t, &m);
	65
fa544fff	66	return spi_sync(nspi->spi, &m);
ee9596d4 FD	67	}
ee9596d4 FD	68
2bed2785 EL	69	int nci_spi_send(struct nci_spi *nspi,
	70	struct completion *write_handshake_completion,
	71	struct sk_buff *skb)
8a00a61b	72	{
ee9596d4 FD	73	unsigned int payload_len = skb->len;
	74	unsigned char *hdr;
	75	int ret;
	76	long completion_rc;
	77
ee9596d4 FD	78	/* add the NCI SPI header to the start of the buffer */
	79	hdr = skb_push(skb, NCI_SPI_HDR_LEN);
	80	hdr[0] = NCI_SPI_DIRECT_WRITE;
fa544fff	81	hdr[1] = nspi->acknowledge_mode;
ee9596d4 FD	82	hdr[2] = payload_len >> 8;
	83	hdr[3] = payload_len & 0xFF;
	84
fa544fff	85	if (nspi->acknowledge_mode == NCI_SPI_CRC_ENABLED) {
ee9596d4 FD	86	u16 crc;
	87
	88	crc = crc_ccitt(CRC_INIT, skb->data, skb->len);
	89	*skb_put(skb, 1) = crc >> 8;
	90	*skb_put(skb, 1) = crc & 0xFF;
	91	}
	92
2bed2785 EL	93	if (write_handshake_completion) {
	94	/* Trick SPI driver to raise chip select */
	95	ret = __nci_spi_send(nspi, NULL, 1);
	96	if (ret)
	97	goto done;
ee9596d4	98
2bed2785 EL	99	/* wait for NFC chip hardware handshake to complete */
	100	if (wait_for_completion_timeout(write_handshake_completion,
	101	msecs_to_jiffies(1000)) == 0) {
	102	ret = -ETIME;
	103	goto done;
	104	}
	105	}
ee9596d4	106
2bed2785	107	ret = __nci_spi_send(nspi, skb, 0);
fa544fff	108	if (ret != 0 \|\| nspi->acknowledge_mode == NCI_SPI_CRC_DISABLED)
ee9596d4 FD	109	goto done;
ee9596d4 FD	110
9bec44bf	111	reinit_completion(&nspi->req_completion);
d5937511	112	completion_rc = wait_for_completion_interruptible_timeout(
fa544fff	113	&nspi->req_completion,
d5937511	114	NCI_SPI_SEND_TIMEOUT);
ee9596d4	115
fa544fff	116	if (completion_rc <= 0 \|\| nspi->req_result == ACKNOWLEDGE_NACK)
ee9596d4 FD	117	ret = -EIO;
	118
	119	done:
2bed2785 EL	120	kfree_skb(skb);
2bed2785 EL	121
ee9596d4	122	return ret;
8a00a61b	123	}
fa544fff	124	EXPORT_SYMBOL_GPL(nci_spi_send);
8a00a61b FD	125
	126	/* ---- Interface to NCI SPI drivers ---- */
	127
	128	/**
fa544fff	129	* nci_spi_allocate_spi - allocate a new nci spi
8a00a61b FD	130	*
8a00a61b FD	131	* @spi: SPI device
fa544fff	132	* @acknowledge_mode: Acknowledge mode used by the NFC device
8a00a61b	133	* @delay: delay between transactions in us
fa544fff	134	* @ndev: nci dev to send incoming nci frames to
8a00a61b	135	*/
fa544fff	136	struct nci_spi nci_spi_allocate_spi(struct spi_device spi,
fa544fff EL	137	u8 acknowledge_mode, unsigned int delay,
fa544fff EL	138	struct nci_dev *ndev)
8a00a61b	139	{
fa544fff	140	struct nci_spi *nspi;
8a00a61b	141
fa544fff EL	142	nspi = devm_kzalloc(&spi->dev, sizeof(struct nci_spi), GFP_KERNEL);
fa544fff EL	143	if (!nspi)
8a00a61b FD	144	return NULL;
8a00a61b FD	145
fa544fff EL	146	nspi->acknowledge_mode = acknowledge_mode;
fa544fff EL	147	nspi->xfer_udelay = delay;
2bd83245 VC	148	/* Use controller max SPI speed by default */
2bd83245 VC	149	nspi->xfer_speed_hz = 0;
645d5087	150	nspi->spi = spi;
fa544fff	151	nspi->ndev = ndev;
9bec44bf	152	init_completion(&nspi->req_completion);
8a00a61b	153
fa544fff	154	return nspi;
8a00a61b	155	}
fa544fff	156	EXPORT_SYMBOL_GPL(nci_spi_allocate_spi);
391d8a2d	157
fa544fff	158	static int send_acknowledge(struct nci_spi *nspi, u8 acknowledge)
391d8a2d FD	159	{
	160	struct sk_buff *skb;
	161	unsigned char *hdr;
	162	u16 crc;
	163	int ret;
	164
fa544fff	165	skb = nci_skb_alloc(nspi->ndev, 0, GFP_KERNEL);
391d8a2d FD	166
	167	/* add the NCI SPI header to the start of the buffer */
	168	hdr = skb_push(skb, NCI_SPI_HDR_LEN);
	169	hdr[0] = NCI_SPI_DIRECT_WRITE;
	170	hdr[1] = NCI_SPI_CRC_ENABLED;
	171	hdr[2] = acknowledge << NCI_SPI_ACK_SHIFT;
	172	hdr[3] = 0;
	173
	174	crc = crc_ccitt(CRC_INIT, skb->data, skb->len);
	175	*skb_put(skb, 1) = crc >> 8;
	176	*skb_put(skb, 1) = crc & 0xFF;
	177
2bed2785	178	ret = __nci_spi_send(nspi, skb, 0);
391d8a2d FD	179
	180	kfree_skb(skb);
	181
	182	return ret;
	183	}
	184
22d4aae5	185	static struct sk_buff __nci_spi_read(struct nci_spi nspi)
391d8a2d FD	186	{
	187	struct sk_buff *skb;
	188	struct spi_message m;
	189	unsigned char req[2], resp_hdr[2];
	190	struct spi_transfer tx, rx;
	191	unsigned short rx_len = 0;
	192	int ret;
	193
	194	spi_message_init(&m);
a4ada6ca EL	195
a4ada6ca EL	196	memset(&tx, 0, sizeof(struct spi_transfer));
391d8a2d	197	req[0] = NCI_SPI_DIRECT_READ;
fa544fff	198	req[1] = nspi->acknowledge_mode;
391d8a2d FD	199	tx.tx_buf = req;
	200	tx.len = 2;
	201	tx.cs_change = 0;
2bd83245	202	tx.speed_hz = nspi->xfer_speed_hz;
391d8a2d	203	spi_message_add_tail(&tx, &m);
a4ada6ca EL	204
a4ada6ca EL	205	memset(&rx, 0, sizeof(struct spi_transfer));
391d8a2d FD	206	rx.rx_buf = resp_hdr;
	207	rx.len = 2;
	208	rx.cs_change = 1;
2bd83245	209	rx.speed_hz = nspi->xfer_speed_hz;
391d8a2d	210	spi_message_add_tail(&rx, &m);
a4ada6ca	211
fa544fff	212	ret = spi_sync(nspi->spi, &m);
391d8a2d FD	213	if (ret)
	214	return NULL;
	215
fa544fff	216	if (nspi->acknowledge_mode == NCI_SPI_CRC_ENABLED)
391d8a2d FD	217	rx_len = ((resp_hdr[0] & NCI_SPI_MSB_PAYLOAD_MASK) << 8) +
	218	resp_hdr[1] + NCI_SPI_CRC_LEN;
	219	else
	220	rx_len = (resp_hdr[0] << 8) \| resp_hdr[1];
	221
fa544fff	222	skb = nci_skb_alloc(nspi->ndev, rx_len, GFP_KERNEL);
391d8a2d FD	223	if (!skb)
	224	return NULL;
	225
	226	spi_message_init(&m);
a4ada6ca EL	227
a4ada6ca EL	228	memset(&rx, 0, sizeof(struct spi_transfer));
391d8a2d FD	229	rx.rx_buf = skb_put(skb, rx_len);
	230	rx.len = rx_len;
	231	rx.cs_change = 0;
fa544fff	232	rx.delay_usecs = nspi->xfer_udelay;
2bd83245	233	rx.speed_hz = nspi->xfer_speed_hz;
391d8a2d	234	spi_message_add_tail(&rx, &m);
a4ada6ca	235
fa544fff	236	ret = spi_sync(nspi->spi, &m);
391d8a2d FD	237	if (ret)
	238	goto receive_error;
	239
fa544fff	240	if (nspi->acknowledge_mode == NCI_SPI_CRC_ENABLED) {
391d8a2d FD	241	*skb_push(skb, 1) = resp_hdr[1];
	242	*skb_push(skb, 1) = resp_hdr[0];
	243	}
	244
	245	return skb;
	246
	247	receive_error:
	248	kfree_skb(skb);
	249
	250	return NULL;
	251	}
	252
	253	static int nci_spi_check_crc(struct sk_buff *skb)
	254	{
	255	u16 crc_data = (skb->data[skb->len - 2] << 8) \|
	256	skb->data[skb->len - 1];
	257	int ret;
	258
	259	ret = (crc_ccitt(CRC_INIT, skb->data, skb->len - NCI_SPI_CRC_LEN)
	260	== crc_data);
	261
	262	skb_trim(skb, skb->len - NCI_SPI_CRC_LEN);
	263
	264	return ret;
	265	}
	266
	267	static u8 nci_spi_get_ack(struct sk_buff *skb)
	268	{
	269	u8 ret;
	270
	271	ret = skb->data[0] >> NCI_SPI_ACK_SHIFT;
	272
	273	/* Remove NFCC part of the header: ACK, NACK and MSB payload len */
	274	skb_pull(skb, 2);
	275
	276	return ret;
	277	}
	278
	279	/**
22d4aae5	280	* nci_spi_read - read frame from NCI SPI drivers
391d8a2d	281	*
fa544fff	282	* @nspi: The nci spi
391d8a2d FD	283	* Context: can sleep
	284	*
	285	* This call may only be used from a context that may sleep. The sleep
	286	* is non-interruptible, and has no timeout.
	287	*
22d4aae5	288	* It returns an allocated skb containing the frame on success, or NULL.
391d8a2d	289	*/
22d4aae5	290	struct sk_buff nci_spi_read(struct nci_spi nspi)
391d8a2d FD	291	{
391d8a2d FD	292	struct sk_buff *skb;
391d8a2d	293
391d8a2d	294	/* Retrieve frame from SPI */
22d4aae5 EL	295	skb = __nci_spi_read(nspi);
22d4aae5 EL	296	if (!skb)
391d8a2d	297	goto done;
391d8a2d	298
fa544fff	299	if (nspi->acknowledge_mode == NCI_SPI_CRC_ENABLED) {
391d8a2d	300	if (!nci_spi_check_crc(skb)) {
fa544fff	301	send_acknowledge(nspi, ACKNOWLEDGE_NACK);
391d8a2d FD	302	goto done;
	303	}
	304
	305	/* In case of acknowledged mode: if ACK or NACK received,
	306	* unblock completion of latest frame sent.
	307	*/
fa544fff EL	308	nspi->req_result = nci_spi_get_ack(skb);
	309	if (nspi->req_result)
	310	complete(&nspi->req_completion);
391d8a2d FD	311	}
	312
	313	/* If there is no payload (ACK/NACK only frame),
	314	* free the socket buffer
	315	*/
22d4aae5	316	if (!skb->len) {
391d8a2d	317	kfree_skb(skb);
22d4aae5	318	skb = NULL;
391d8a2d FD	319	goto done;
	320	}
	321
fa544fff EL	322	if (nspi->acknowledge_mode == NCI_SPI_CRC_ENABLED)
fa544fff EL	323	send_acknowledge(nspi, ACKNOWLEDGE_ACK);
391d8a2d	324
391d8a2d	325	done:
391d8a2d	326
22d4aae5	327	return skb;
391d8a2d	328	}
22d4aae5	329	EXPORT_SYMBOL_GPL(nci_spi_read);
fcd9d046 VC	330
fcd9d046 VC	331	MODULE_LICENSE("GPL");