From 48164754d7fe219911b7653449a4ce85d23c3556 Mon Sep 17 00:00:00 2001 From: Ian Abbott Date: Wed, 31 Oct 2018 12:29:56 +0000 Subject: [PATCH] staging: comedi: addi_apci_3501: Use insn->n in EEPROM insn_read handler The `insn_read` handler for the EEPROM subdevice (`apci3501_eeprom_insn_read()`) currently ignores `insn->n` (the number of samples to be read) and assumes a single sample is to be read. But `insn->n` could be 0, meaning no samples should be read, in which case `data[0]` ought not to be written. (The comedi core at least ensures that `data[0]` exists, but we should not rely on that.) Following the usual Comedi guidelines and interpret `insn->n` as the number of samples to be read, but only read the EEPROM location once and make `insn->n` copies, as we don't expect the contents of the EEPROM location to change between readings. Signed-off-by: Ian Abbott Signed-off-by: Greg Kroah-Hartman --- drivers/staging/comedi/drivers/addi_apci_3501.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/drivers/staging/comedi/drivers/addi_apci_3501.c b/drivers/staging/comedi/drivers/addi_apci_3501.c index a382679..b4aa588 100644 --- a/drivers/staging/comedi/drivers/addi_apci_3501.c +++ b/drivers/staging/comedi/drivers/addi_apci_3501.c @@ -258,8 +258,15 @@ static int apci3501_eeprom_insn_read(struct comedi_device *dev, { struct apci3501_private *devpriv = dev->private; unsigned short addr = CR_CHAN(insn->chanspec); + unsigned int val; + unsigned int i; - data[0] = apci3501_eeprom_readw(devpriv->amcc, 2 * addr); + if (insn->n) { + /* No point reading the same EEPROM location more than once. */ + val = apci3501_eeprom_readw(devpriv->amcc, 2 * addr); + for (i = 0; i < insn->n; i++) + data[i] = val; + } return insn->n; } -- 2.7.4