From b33fc68c26a56d23b7221434dd367949420637bc Mon Sep 17 00:00:00 2001 From: Ian Abbott Date: Tue, 30 Oct 2018 14:17:12 +0000 Subject: [PATCH] staging: comedi: cb_pcidas64: Use insn->n in EEPROM insn_read handler The `insn_read` handler for the EEPROM subdevice (`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.) Follow 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/cb_pcidas64.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) diff --git a/drivers/staging/comedi/drivers/cb_pcidas64.c b/drivers/staging/comedi/drivers/cb_pcidas64.c index 44e5aaf..e1774e0 100644 --- a/drivers/staging/comedi/drivers/cb_pcidas64.c +++ b/drivers/staging/comedi/drivers/cb_pcidas64.c @@ -3768,9 +3768,17 @@ static int eeprom_read_insn(struct comedi_device *dev, struct comedi_subdevice *s, struct comedi_insn *insn, unsigned int *data) { - data[0] = read_eeprom(dev, CR_CHAN(insn->chanspec)); + unsigned int val; + unsigned int i; - return 1; + if (insn->n) { + /* No point reading the same EEPROM location more than once. */ + val = read_eeprom(dev, CR_CHAN(insn->chanspec)); + for (i = 0; i < insn->n; i++) + data[i] = val; + } + + return insn->n; } /* Allocate and initialize the subdevice structures. */ -- 2.7.4