diff options
| author | Samuel Ortiz <sameo@linux.intel.com> | 2013-07-03 15:14:17 +0200 |
|---|---|---|
| committer | Samuel Ortiz <sameo@linux.intel.com> | 2013-08-14 00:35:19 +0200 |
| commit | dfccd0f580445d176acea174175b3e6518cc91f7 (patch) | |
| tree | 9685d2c41e53be5b254bcaf26ccb54b116ea1ea5 | |
| parent | 46f793b0413cfb234ca4faf7e598f24967e1fd3b (diff) | |
NFC: pn533: Add some polling entropy
By not always starting the polling loop from the same modulation, we
avoid entering infinite loops where devices exporting 2 targets (on 2
different modulations) get the same target activated over and over.
If this target is not readable (e.g. a wallet emulating a tag), we will
stay in an error loop for ever.
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>
| -rw-r--r-- | drivers/nfc/pn533.c | 7 |
1 files changed, 6 insertions, 1 deletions
diff --git a/drivers/nfc/pn533.c b/drivers/nfc/pn533.c index 9f3868b0170..5df730be88a 100644 --- a/drivers/nfc/pn533.c +++ b/drivers/nfc/pn533.c @@ -1913,6 +1913,7 @@ static int pn533_start_poll(struct nfc_dev *nfc_dev, u32 im_protocols, u32 tm_protocols) { struct pn533 *dev = nfc_get_drvdata(nfc_dev); + u8 rand_mod; nfc_dev_dbg(&dev->interface->dev, "%s: im protocols 0x%x tm protocols 0x%x", @@ -1936,11 +1937,15 @@ static int pn533_start_poll(struct nfc_dev *nfc_dev, tm_protocols = 0; } - dev->poll_mod_curr = 0; pn533_poll_create_mod_list(dev, im_protocols, tm_protocols); dev->poll_protocols = im_protocols; dev->listen_protocols = tm_protocols; + /* Do not always start polling from the same modulation */ + get_random_bytes(&rand_mod, sizeof(rand_mod)); + rand_mod %= dev->poll_mod_count; + dev->poll_mod_curr = rand_mod; + return pn533_send_poll_frame(dev); } |