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    SubjectRe: [PATCH v4] tpm: fix reference counting for struct tpm_chip
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    Hi,

    On 16.02.21 at 13:53, Jason Gunthorpe wrote:
    > On Tue, Feb 16, 2021 at 01:31:00AM +0100, Lino Sanfilippo wrote:
    >>
    >> +static int tpm_add_tpm2_char_device(struct tpm_chip *chip)
    >> +{
    >> + int rc;
    >> +
    >> + device_initialize(&chip->devs);
    >> + chip->devs.parent = chip->dev.parent;
    >> + chip->devs.class = tpmrm_class;
    >> +
    >> + rc = dev_set_name(&chip->devs, "tpmrm%d", chip->dev_num);
    >> + if (rc)
    >> + goto out_put_devs;
    >> + /*
    >> + * get extra reference on main device to hold on behalf of devs.
    >> + * This holds the chip structure while cdevs is in use. The
    >> + * corresponding put is in the tpm_devs_release.
    >> + */
    >> + get_device(&chip->dev);
    >> + chip->devs.release = tpm_devs_release;
    >> + chip->devs.devt =
    >> + MKDEV(MAJOR(tpm_devt), chip->dev_num + TPM_NUM_DEVICES);
    >> + cdev_init(&chip->cdevs, &tpmrm_fops);
    >> + chip->cdevs.owner = THIS_MODULE;
    >> +
    >> + rc = cdev_device_add(&chip->cdevs, &chip->devs);
    >> + if (rc) {
    >> + dev_err(&chip->devs,
    >> + "unable to cdev_device_add() %s, major %d, minor %d, err=%d\n",
    >> + dev_name(&chip->devs), MAJOR(chip->devs.devt),
    >> + MINOR(chip->devs.devt), rc);
    >> + goto out_put_devs;
    >> + }
    >> +
    >> + return 0;
    >> +
    >> +out_put_devs:
    >> + put_device(&chip->devs);
    >
    > I'd rather you organize this so chip->devs.release and the get_device
    > is always sent instead of having the possiblity for a put_device that
    > doesn't call release
    >

    Agreed, I will change it. It should not make a difference in terms of correctness
    but I see that it is less confusing if both error cases are handled similarly (plus its
    only a minimal change).


    Best regards,
    Lino

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