On Fri, Jun 22, 2018 at 04:45:47PM -0400, Stefan Berger wrote:
> On 06/22/2018 04:43 PM, Jason Gunthorpe wrote:
> >On Fri, Jun 22, 2018 at 12:46:11PM -0400, Stefan Berger wrote:
> >>Implement tpm_chip_find() for other subsystems to find a TPM chip and
> >>get a reference to that chip.
> >>
> >>Signed-off-by: Stefan Berger <[email protected]>
> >> drivers/char/tpm/tpm-chip.c | 27 +++++++++++++++++++++++++++
> >> include/linux/tpm.h | 5 +++++
> >> 2 files changed, 32 insertions(+)
> >>
> >>diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c
> >>index 4e83695af068..2520555b1e17 100644
> >>+++ b/drivers/char/tpm/tpm-chip.c
> >>@@ -81,6 +81,33 @@ void tpm_put_ops(struct tpm_chip *chip)
> >> EXPORT_SYMBOL_GPL(tpm_put_ops);
> >> /**
> >>+ * tpm_chip_find() - find a TPM chip and get a reference to it
> >>+ */
> >>+struct tpm_chip *tpm_chip_find(void)
> >I feel like this should be called 'tpm_default_chip()'
> >
> >>+{
> >>+ struct tpm_chip *chip, *res = NULL;
> >>+ int chip_num = 0;
> >>+ int chip_prev;
> >>+
> >>+ mutex_lock(&idr_lock);
> >>+
> >>+ do {
> >>+ chip_prev = chip_num;
> >>+ chip = idr_get_next(&dev_nums_idr, &chip_num);
> >>+ if (chip) {
> >>+ get_device(&chip->dev);
> >>+ res = chip;
> >>+ break;
> >>+ }
> >>+ } while (chip_prev != chip_num);
> >>+
> >>+ mutex_unlock(&idr_lock);
> >And what was tpm_chip_find_get should just call this function..
> And then after that each time tpm_get_ops() ?
It is best to keep the tpm_chip_find_get/tpm_put_ops for internal use
as it also manages the kref lifetime of chip in a subtle way, it
relies on the ops lock not the kref to keep the memory valid when it
has a NULL parameter..
Something like this:
struct tpm_chip *tpm_find_get_ops(struct tpm_chip *chip)
{
int rc;
if (chip) {
if (!tpm_try_get_ops(chip))
return NULL;
return chip;
}
chip = tpm_default_chip();
rc = tpm_try_get_ops(chip));
put_device(&chip->dev);
if (rc)
return NULL;
return chip;
}
Jason
