Re: [PATCH v2] tpm: use struct tpm_chip for tpm_chip_find_get()

[Jason Gunthorpe]

> struct tpm_chip *tpm_chip_find_get(u64 id)
> {
>       struct tpm_chup *chip;
>       struct tpm_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 && (!id || id == chip->id) && !tpm_try_get_ops(chip)) {
>                       res = chip;
>                       break;
>               }
>       } while (chip_prev != chip_num);
> 
>       mutex_unlock(&idr_lock);
> 
>       return res;
> }

?? The old version was correct, idr_find_slowpath is better than an
idr_get_next serach if you already know id.

PrasannaKumar's solution seems right, if we already have chip, then we
just need to lock it again:

struct tpm_chip *tpm_chip_find_get(struct tpm_chip *chip)
{
        struct tpm_chip *res = NULL;

        mutex_lock(&idr_lock);

        if (!chip) {
                int chip_num = 0;
                int chip_prev;

                do {
                        chip_prev = chip_num;
                        chip = idr_get_next(&dev_nums_idr, &chip_num);
                        if (chip && !tpm_try_get_ops(chip)) {
                                res = chip;
                                break;
                        }
                } while (chip_prev != chip_num);
        } else {
                if (!tpm_try_get_ops(chip))
                        res = chip;
        }

        mutex_unlock(&idr_lock);

        return res;
}

Jason