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NFC: Modified hci_transceive to become an asynchronous operation
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This enables the completion callback to be called from a different
context, preventing a possible deadlock if the callback resulted in the
invocation of a nested call to the currently locked nfc_dev.
This is also more in line with the im_transceive nfc_ops for NFC Core or
NCI drivers which already behave asynchronously.

Signed-off-by: Eric Lapuyade <eric.lapuyade@intel.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>
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Eric Lapuyade authored and Samuel Ortiz committed Sep 24, 2012
1 parent e4c4789 commit f3e8fb5
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Showing 5 changed files with 92 additions and 39 deletions.
57 changes: 42 additions & 15 deletions drivers/nfc/pn544_hci.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -148,6 +148,9 @@ struct pn544_hci_info {
* < 0 if hardware error occured (e.g. i2c err)
* and prevents normal operation.
*/
int async_cb_type;
data_exchange_cb_t async_cb;
void *async_cb_context;
};

static void pn544_hci_platform_init(struct pn544_hci_info *info)
Expand Down Expand Up @@ -731,6 +734,26 @@ static int pn544_hci_complete_target_discovered(struct nfc_shdlc *shdlc,
return r;
}

#define PN544_CB_TYPE_READER_F 1

static void pn544_hci_data_exchange_cb(void *context, struct sk_buff *skb,
int err)
{
struct pn544_hci_info *info = context;

switch (info->async_cb_type) {
case PN544_CB_TYPE_READER_F:
if (err == 0)
skb_pull(skb, 1);
info->async_cb(info->async_cb_context, skb, err);
break;
default:
if (err == 0)
kfree_skb(skb);
break;
}
}

#define MIFARE_CMD_AUTH_KEY_A 0x60
#define MIFARE_CMD_AUTH_KEY_B 0x61
#define MIFARE_CMD_HEADER 2
Expand All @@ -744,11 +767,11 @@ static int pn544_hci_complete_target_discovered(struct nfc_shdlc *shdlc,
*/
static int pn544_hci_data_exchange(struct nfc_shdlc *shdlc,
struct nfc_target *target,
struct sk_buff *skb,
struct sk_buff **res_skb)
struct sk_buff *skb, data_exchange_cb_t cb,
void *cb_context)
{
struct pn544_hci_info *info = nfc_shdlc_get_clientdata(shdlc);
struct nfc_hci_dev *hdev = nfc_shdlc_get_hci_dev(shdlc);
int r;

pr_info(DRIVER_DESC ": %s for gate=%d\n", __func__,
target->hci_reader_gate);
Expand All @@ -773,25 +796,29 @@ static int pn544_hci_data_exchange(struct nfc_shdlc *shdlc,
memcpy(data, uid, MIFARE_UID_LEN);
}

return nfc_hci_send_cmd(hdev, target->hci_reader_gate,
PN544_MIFARE_CMD,
skb->data, skb->len, res_skb);
return nfc_hci_send_cmd_async(hdev,
target->hci_reader_gate,
PN544_MIFARE_CMD,
skb->data, skb->len,
cb, cb_context);
} else
return 1;
case PN544_RF_READER_F_GATE:
*skb_push(skb, 1) = 0;
*skb_push(skb, 1) = 0;

r = nfc_hci_send_cmd(hdev, target->hci_reader_gate,
PN544_FELICA_RAW,
skb->data, skb->len, res_skb);
if (r == 0)
skb_pull(*res_skb, 1);
return r;
info->async_cb_type = PN544_CB_TYPE_READER_F;
info->async_cb = cb;
info->async_cb_context = cb_context;

return nfc_hci_send_cmd_async(hdev, target->hci_reader_gate,
PN544_FELICA_RAW, skb->data,
skb->len,
pn544_hci_data_exchange_cb, info);
case PN544_RF_READER_JEWEL_GATE:
return nfc_hci_send_cmd(hdev, target->hci_reader_gate,
PN544_JEWEL_RAW_CMD,
skb->data, skb->len, res_skb);
return nfc_hci_send_cmd_async(hdev, target->hci_reader_gate,
PN544_JEWEL_RAW_CMD, skb->data,
skb->len, cb, cb_context);
default:
return 1;
}
Expand Down
8 changes: 6 additions & 2 deletions include/net/nfc/hci.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -38,8 +38,8 @@ struct nfc_hci_ops {
int (*complete_target_discovered) (struct nfc_hci_dev *hdev, u8 gate,
struct nfc_target *target);
int (*data_exchange) (struct nfc_hci_dev *hdev,
struct nfc_target *target,
struct sk_buff *skb, struct sk_buff **res_skb);
struct nfc_target *target, struct sk_buff *skb,
data_exchange_cb_t cb, void *cb_context);
int (*check_presence)(struct nfc_hci_dev *hdev,
struct nfc_target *target);
};
Expand Down Expand Up @@ -103,6 +103,10 @@ struct nfc_hci_dev {
u8 hw_mpw;
u8 hw_software;
u8 hw_bsid;

int async_cb_type;
data_exchange_cb_t async_cb;
void *async_cb_context;
};

/* hci device allocation */
Expand Down
4 changes: 2 additions & 2 deletions include/net/nfc/shdlc.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -34,8 +34,8 @@ struct nfc_shdlc_ops {
int (*complete_target_discovered) (struct nfc_shdlc *shdlc, u8 gate,
struct nfc_target *target);
int (*data_exchange) (struct nfc_shdlc *shdlc,
struct nfc_target *target,
struct sk_buff *skb, struct sk_buff **res_skb);
struct nfc_target *target, struct sk_buff *skb,
data_exchange_cb_t cb, void *cb_context);
int (*check_presence)(struct nfc_shdlc *shdlc,
struct nfc_target *target);
};
Expand Down
57 changes: 39 additions & 18 deletions net/nfc/hci/core.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -537,54 +537,75 @@ static void hci_deactivate_target(struct nfc_dev *nfc_dev,
{
}

#define HCI_CB_TYPE_TRANSCEIVE 1

static void hci_transceive_cb(void *context, struct sk_buff *skb, int err)
{
struct nfc_hci_dev *hdev = context;

switch (hdev->async_cb_type) {
case HCI_CB_TYPE_TRANSCEIVE:
/*
* TODO: Check RF Error indicator to make sure data is valid.
* It seems that HCI cmd can complete without error, but data
* can be invalid if an RF error occured? Ignore for now.
*/
if (err == 0)
skb_trim(skb, skb->len - 1); /* RF Err ind */

hdev->async_cb(hdev->async_cb_context, skb, err);
break;
default:
if (err == 0)
kfree_skb(skb);
break;
}
}

static int hci_transceive(struct nfc_dev *nfc_dev, struct nfc_target *target,
struct sk_buff *skb, data_exchange_cb_t cb,
void *cb_context)
{
struct nfc_hci_dev *hdev = nfc_get_drvdata(nfc_dev);
int r;
struct sk_buff *res_skb = NULL;

pr_debug("target_idx=%d\n", target->idx);

switch (target->hci_reader_gate) {
case NFC_HCI_RF_READER_A_GATE:
case NFC_HCI_RF_READER_B_GATE:
if (hdev->ops->data_exchange) {
r = hdev->ops->data_exchange(hdev, target, skb,
&res_skb);
r = hdev->ops->data_exchange(hdev, target, skb, cb,
cb_context);
if (r <= 0) /* handled */
break;
}

*skb_push(skb, 1) = 0; /* CTR, see spec:10.2.2.1 */
r = nfc_hci_send_cmd(hdev, target->hci_reader_gate,
NFC_HCI_WR_XCHG_DATA,
skb->data, skb->len, &res_skb);
/*
* TODO: Check RF Error indicator to make sure data is valid.
* It seems that HCI cmd can complete without error, but data
* can be invalid if an RF error occured? Ignore for now.
*/
if (r == 0)
skb_trim(res_skb, res_skb->len - 1); /* RF Err ind */

hdev->async_cb_type = HCI_CB_TYPE_TRANSCEIVE;
hdev->async_cb = cb;
hdev->async_cb_context = cb_context;

r = nfc_hci_send_cmd_async(hdev, target->hci_reader_gate,
NFC_HCI_WR_XCHG_DATA, skb->data,
skb->len, hci_transceive_cb, hdev);
break;
default:
if (hdev->ops->data_exchange) {
r = hdev->ops->data_exchange(hdev, target, skb,
&res_skb);
r = hdev->ops->data_exchange(hdev, target, skb, cb,
cb_context);
if (r == 1)
r = -ENOTSUPP;
}
else
r = -ENOTSUPP;
break;
}

kfree_skb(skb);

cb(cb_context, res_skb, r);

return 0;
return r;
}

static int hci_check_presence(struct nfc_dev *nfc_dev,
Expand Down
5 changes: 3 additions & 2 deletions net/nfc/hci/shdlc.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -777,12 +777,13 @@ static int nfc_shdlc_complete_target_discovered(struct nfc_hci_dev *hdev,
static int nfc_shdlc_data_exchange(struct nfc_hci_dev *hdev,
struct nfc_target *target,
struct sk_buff *skb,
struct sk_buff **res_skb)
data_exchange_cb_t cb, void *cb_context)
{
struct nfc_shdlc *shdlc = nfc_hci_get_clientdata(hdev);

if (shdlc->ops->data_exchange)
return shdlc->ops->data_exchange(shdlc, target, skb, res_skb);
return shdlc->ops->data_exchange(shdlc, target, skb, cb,
cb_context);

return -EPERM;
}
Expand Down

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