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    SubjectRe: [PATCH] tpm: remove type and name fields from the I2C Infineon OF table entries
    Hi

    Some basic questions about DT, which I'm not expert of.

    On Mon, Dec 04, 2017 at 06:39:16PM +0100, Javier Martinez Canillas wrote:
    > The commit 21dc02eab989 ("tpm/tpm_i2c_infineon.c: Add OF attributes type
    > and name to the of_device_id table entries") added type and name fields
    > to the OF device ID table entries for the I2C Infineon TPM driver.
    >
    > The only justification for the change in the commit message is that it's
    > probably a good idea to have these fields populated in the OF entries.
    >
    > But I don't think that's true. In fact, I believe that's not correct to
    > add these fields for the following reasons:
    >
    > * The struct of_device_id .type field matches the device_type property
    > in the Device Tree nodes. The ePAPR document says that new use of the
    > property is deprecated and should only be included in cpu and memory
    > nodes for compatibility with the IEEE 1275-derived Device Trees.
    > Also, mainline Device Tree source files don't include this property
    > in the TPM nodes defined.
    >
    > * The struct of_device_id .name field matches the Device Tree node name
    > but the ePAPR document says that the node name should be generic and
    > reflect the function of the device, not it's programming model. So in
    > the case of TPM chips, it should just be "tpm" but the name fields are
    > set in the OF table entries to the actual device model (i.e: slb9645tt).

    So why the name field is not changed to "tpm"?

    > Now, from a practical point of view this means that the OF module aliases
    > for the supported devices include the name and type of the device entries:
    >
    > $ modinfo drivers/char/tpm/tpm_i2c_infineon.ko | grep alias
    > alias: of:Nslb9645ttTtpm*Cinfineon,slb9645ttC*
    > alias: of:Nslb9645ttTtpm*Cinfineon,slb9645tt
    > alias: of:Nslb9635ttTtpm*Cinfineon,slb9635ttC*
    > alias: of:Nslb9635ttTtpm*Cinfineon,slb9635tt
    > alias: of:Ntpm_i2c_infineonTtpm*Cinfineon,tpm_i2c_infineonC*
    > alias: of:Ntpm_i2c_infineonTtpm*Cinfineon,tpm_i2c_infineon
    >
    > But since the device_type isn't set in the tpm DT nodes and the node name
    > is a generic one, the reported MODALIAS when a device is registered via OF
    > won't match the driver's module aliases:
    >
    > $ cat /sys/class/tpm/tpm0/device/modalias
    > of:NtpmT<NULL>Cinfineon,slb9645tt
    >
    > So remove these fields from the OF entries to allow the module aliases to
    > match the MODALIAS reported by the kernel when the device is registered:
    >
    > $ modinfo drivers/char/tpm/tpm_i2c_infineon.ko | grep alias
    > alias: of:N*T*Cinfineon,slb9645ttC*
    > alias: of:N*T*Cinfineon,slb9645tt
    > alias: of:N*T*Cinfineon,slb9635ttC*
    > alias: of:N*T*Cinfineon,slb9635tt
    > alias: of:N*T*Cinfineon,tpm_i2c_infineonC*
    > alias: of:N*T*Cinfineon,tpm_i2c_infineon
    >
    > Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>
    > ---
    >
    > drivers/char/tpm/tpm_i2c_infineon.c | 21 +++------------------
    > 1 file changed, 3 insertions(+), 18 deletions(-)
    >
    > diff --git a/drivers/char/tpm/tpm_i2c_infineon.c b/drivers/char/tpm/tpm_i2c_infineon.c
    > index 79d6bbb58e39..005c38879b2e 100644
    > --- a/drivers/char/tpm/tpm_i2c_infineon.c
    > +++ b/drivers/char/tpm/tpm_i2c_infineon.c
    > @@ -675,24 +675,9 @@ MODULE_DEVICE_TABLE(i2c, tpm_tis_i2c_table);
    >
    > #ifdef CONFIG_OF
    > static const struct of_device_id tpm_tis_i2c_of_match[] = {
    > - {
    > - .name = "tpm_i2c_infineon",
    > - .type = "tpm",
    > - .compatible = "infineon,tpm_i2c_infineon",
    > - .data = (void *)0
    > - },
    > - {
    > - .name = "slb9635tt",
    > - .type = "tpm",
    > - .compatible = "infineon,slb9635tt",
    > - .data = (void *)0
    > - },
    > - {
    > - .name = "slb9645tt",
    > - .type = "tpm",
    > - .compatible = "infineon,slb9645tt",
    > - .data = (void *)1
    > - },
    > + { .compatible = "infineon,tpm_i2c_infineon", .data = (void *)0 },
    > + { .compatible = "infineon,slb9635tt", .data = (void *)0 },
    > + { .compatible = "infineon,slb9645tt", .data = (void *)1 },
    > {},
    > };
    > MODULE_DEVICE_TABLE(of, tpm_tis_i2c_of_match);
    > --
    > 2.14.3
    >

    What does the "data" field mean?

    /Jarkko

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