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Date: Fri, 30 Jan 2009 12:43:59 -0200
From: Rajiv Andrade <srajiv@...ux.vnet.ibm.com>
To: Matt Helsley <matthltc@...ibm.com>
CC: linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
dave@...ux.vnet.ibm.com, jmorris@...ei.org,
zohar@...ux.vnet.ibm.com
Subject: Re: [PATCH 1/2] TPM: sysfs functions consolidation
Matt Helsley wrote:
> On Thu, 2009-01-29 at 21:01 -0200, Rajiv Andrade wrote:
>
>> According to Dave Hansen's comments on the tpm_show_*, some of these functions
>> present a pattern when allocating data[] memory space and also when setting its
>> content. A new function was created so that this pattern could be consolidated.
>> Also, replaced the data[] command vectors and its indexes by meaningful structures
>> as pointed out by Matt Helsley too.
>>
>> Signed-off-by: Rajiv Andrade <srajiv@...ux.vnet.ibm.com>
>> ---
>> drivers/char/tpm/tpm.c | 410 +++++++++++++++++-------------------------------
>> drivers/char/tpm/tpm.h | 117 ++++++++++++++
>> 2 files changed, 258 insertions(+), 269 deletions(-)
>>
>> diff --git a/drivers/char/tpm/tpm.c b/drivers/char/tpm/tpm.c
>> index 9c47dc4..58ea16f 100644
>> --- a/drivers/char/tpm/tpm.c
>> +++ b/drivers/char/tpm/tpm.c
>>
>
> <snip>
>
>
>> - rc = transmit_cmd(chip, data, sizeof(data),
>> + rc = transmit_cmd(chip, &tpm_cmd, TPM_INTERNAL_RESULT_SIZE,
>> "attempting to determine the timeouts");
>> if (rc)
>> goto duration;
>>
>> - if (be32_to_cpu(*((__be32 *) (data + TPM_GET_CAP_RET_SIZE_IDX)))
>> + if (be32_to_cpu(tpm_cmd.header.out.length)
>> != 4 * sizeof(u32))
>> goto duration;
>>
>> + timeout_cap = &tpm_cmd.params.getcap_out.cap.timeout;
>> /* Don't overwrite default if value is 0 */
>> - timeout =
>> - be32_to_cpu(*((__be32 *) (data + TPM_GET_CAP_RET_UINT32_1_IDX)));
>> + timeout = be32_to_cpu(timeout_cap->a);
>> if (timeout)
>> chip->vendor.timeout_a = usecs_to_jiffies(timeout);
>> - timeout =
>> - be32_to_cpu(*((__be32 *) (data + TPM_GET_CAP_RET_UINT32_2_IDX)));
>> + timeout = be32_to_cpu(timeout_cap->b);
>> if (timeout)
>> chip->vendor.timeout_b = usecs_to_jiffies(timeout);
>> - timeout =
>> - be32_to_cpu(*((__be32 *) (data + TPM_GET_CAP_RET_UINT32_3_IDX)));
>> + timeout = be32_to_cpu(timeout_cap->c);
>> if (timeout)
>> chip->vendor.timeout_c = usecs_to_jiffies(timeout);
>> - timeout =
>> - be32_to_cpu(*((__be32 *) (data + TPM_GET_CAP_RET_UINT32_4_IDX)));
>> + timeout = be32_to_cpu(timeout_cap->d);
>> if (timeout)
>> chip->vendor.timeout_d = usecs_to_jiffies(timeout);
>>
>
> Are jiffies really the appropriate units of time for the needs of this
> driver? I could easily be wrong but I thought most drivers were
> discouraged from using jiffies since HZ is configurable...
>
>
The timeout is converted from usecs to jiffies before assigning it to
chip->vendor.timeout_*, so even with boxes with different configured HZ,
those values would be the same in usecs.
Hopefully there's no way to modify HZ in runtime.
>> duration:
>> - memcpy(data, tpm_cap, sizeof(tpm_cap));
>> - data[TPM_CAP_IDX] = TPM_CAP_PROP;
>> - data[TPM_CAP_SUBCAP_IDX] = TPM_CAP_PROP_TIS_DURATION;
>> + tpm_cmd.header.in = tpm_getcap_header;
>> + tpm_cmd.params.getcap_in.cap = TPM_CAP_PROP;
>> + tpm_cmd.params.getcap_in.subcap_size = cpu_to_be32(4);
>> + tpm_cmd.params.getcap_in.subcap = TPM_CAP_PROP_TIS_DURATION;
>>
>> - rc = transmit_cmd(chip, data, sizeof(data),
>> + rc = transmit_cmd(chip, &tpm_cmd, TPM_INTERNAL_RESULT_SIZE,
>> "attempting to determine the durations");
>> if (rc)
>> return;
>>
>> - if (be32_to_cpu(*((__be32 *) (data + TPM_GET_CAP_RET_SIZE_IDX)))
>> + if (be32_to_cpu(tpm_cmd.header.out.return_code)
>> != 3 * sizeof(u32))
>> return;
>> -
>> + timeout_cap = &tpm_cmd.params.getcap_out.cap.timeout;
>> chip->vendor.duration[TPM_SHORT] =
>> - usecs_to_jiffies(be32_to_cpu
>> - (*((__be32 *) (data +
>> - TPM_GET_CAP_RET_UINT32_1_IDX))));
>> + usecs_to_jiffies(be32_to_cpu(timeout_cap->a));
>> /* The Broadcom BCM0102 chipset in a Dell Latitude D820 gets the above
>> * value wrong and apparently reports msecs rather than usecs. So we
>> * fix up the resulting too-small TPM_SHORT value to make things work.
>> @@ -565,13 +578,9 @@ duration:
>> chip->vendor.duration[TPM_SHORT] = HZ;
>>
>> chip->vendor.duration[TPM_MEDIUM] =
>> - usecs_to_jiffies(be32_to_cpu
>> - (*((__be32 *) (data +
>> - TPM_GET_CAP_RET_UINT32_2_IDX))));
>> + usecs_to_jiffies(be32_to_cpu(timeout_cap->b));
>> chip->vendor.duration[TPM_LONG] =
>> - usecs_to_jiffies(be32_to_cpu
>> - (*((__be32 *) (data +
>> - TPM_GET_CAP_RET_UINT32_3_IDX))));
>> + usecs_to_jiffies(be32_to_cpu(timeout_cap->c));
>>
>
> OK, so it looks like these timeouts are short, medium, and long-duration
> timeouts and those correspond to "a", "b", and "c". What's "d"? Also
> this suggests slightly-better names for these fields. If you can think
> of short names suggesting why these separate, varying-length timeouts
> are needed that could be even better.
>
> <snip>
>
>
Yes, the timeout_cap struct isn't appropriate here to read the
TIS_DURATION capability, which has a different meaning from the timeout
one and hasn't a forth field to be assigned. I'll write the duration_cap
struct and make use of it here and resubmit this patch.
>> diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h
>> index 8e30df4..867987d 100644
>> --- a/drivers/char/tpm/tpm.h
>> +++ b/drivers/char/tpm/tpm.h
>>
>
> <snip>
>
>
>> +struct timeout_t {
>> + __be32 a;
>> + __be32 b;
>> + __be32 c;
>> + __be32 d;
>> +}__attribute__((packed));
>>
>
> As I pointed out above I think these could use better names. I also
> noticed that there are timeout_a, timeout_b, etc. fields of another
> struct (somewhere under "chips" if I recall..). Perhaps similar naming
> -- maybe even this struct -- should be (re)used?
>
> <snip>
>
>
Yes, it's inside tpm_vendor_specific struct, but this one has __be32
fields. The tpm_vendor_specific struct has these timeout fields and but
also a bunch of others, so unfortunately no reuse could be done.
Thanks reviewing it,
Rajiv
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