Re: [PATCH 2/2] tpm/tpm_ftpm_tee: use send_recv() op

[Jarkko Sakkinen <jarkko@kernel.org>]

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On Wed, Mar 26, 2025 at 04:57:47PM +0200, Jarkko Sakkinen wrote:
> On Wed, Mar 26, 2025 at 11:34:01AM -0300, Jason Gunthorpe wrote:
> > On Wed, Mar 26, 2025 at 02:11:12PM +0200, Jarkko Sakkinen wrote:
> > 
> > > Generally speaking I don't see enough value in complicating
> > > callback interface. It's better to handle complications in
> > > the leaves (i.e. dictatorship of majority ;-) ).
> > 
> > That is very much not the way most driver subsystems view the
> > world. We want to pull logical things into the core code and remove
> > them from drivers to make the drivers simpler and more robust.
> > 
> > The amount of really dumb driver boiler plate that this series
> > obviously removes is exactly the sort of stuff we should be fixing by
> > improving the core code.
> > 
> > The callback interface was never really sanely designed, it was just
> > built around the idea of pulling the timout processing into the core
> > code for TIS hardware. It should be revised to properly match these
> > new HW types that don't have this kind of timeout mechanism.
> 
> Both TIS and CRB, which are TCG standards and they span to many
> different types of drivers and busses. I don't have the figures but
> probably they cover vast majority of the hardware.
> 
> We are talking about 39 lines of reduced complexity at the cost
> of complicating branching at the top level. I doubt that there
> is either any throughput or latency issues.
> 
> What is measurable benefit? The rationale is way way too abstract
> for me to cope, sorry.

E.g., here's how you can get rid of extra cruft in tpm_ftpm_tee w/o
any new callbacks.

BR, Jarkko

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From 1125e80ea274a5ec5d5dba32bfce716ce62c5e4a Mon Sep 17 00:00:00 2001
From: Jarkko Sakkinen <jarkko@kernel.org>
Date: Wed, 26 Mar 2025 17:55:49 +0200
Subject: [PATCH] tpm: Make chip->{status,cancel,req_canceled} opt

tpm_ftpm_tee does not require chip->status, chip->cancel and
chip->req_canceled. Make them optional.

Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
---
 drivers/char/tpm/tpm-interface.c | 31 ++++++++++++++++++++++++++++---
 drivers/char/tpm/tpm_ftpm_tee.c  | 18 ------------------
 2 files changed, 28 insertions(+), 21 deletions(-)

diff --git a/drivers/char/tpm/tpm-interface.c b/drivers/char/tpm/tpm-interface.c
index f62f7871edbd..10ba47a882d8 100644
--- a/drivers/char/tpm/tpm-interface.c
+++ b/drivers/char/tpm/tpm-interface.c
@@ -58,6 +58,30 @@ unsigned long tpm_calc_ordinal_duration(struct tpm_chip *chip, u32 ordinal)
 }
 EXPORT_SYMBOL_GPL(tpm_calc_ordinal_duration);
 
+static void tpm_chip_cancel(struct tpm_chip *chip)
+{
+	if (!chip->ops->cancel)
+		return;
+
+	chip->ops->cancel(chip);
+}
+
+static u8 tpm_chip_status(struct tpm_chip *chip)
+{
+	if (!chip->ops->status)
+		return 0;
+
+	return chip->ops->status(chip);
+}
+
+static bool tpm_chip_req_canceled(struct tpm_chip *chip, u8 status)
+{
+	if (!chip->ops->req_canceled)
+		return false;
+
+	return chip->ops->req_canceled(chip, status);
+}
+
 static ssize_t tpm_try_transmit(struct tpm_chip *chip, void *buf, size_t bufsiz)
 {
 	struct tpm_header *header = buf;
@@ -65,6 +89,7 @@ static ssize_t tpm_try_transmit(struct tpm_chip *chip, void *buf, size_t bufsiz)
 	ssize_t len = 0;
 	u32 count, ordinal;
 	unsigned long stop;
+	u8 status;
 
 	if (bufsiz < TPM_HEADER_SIZE)
 		return -EINVAL;
@@ -104,12 +129,12 @@ static ssize_t tpm_try_transmit(struct tpm_chip *chip, void *buf, size_t bufsiz)
 
 	stop = jiffies + tpm_calc_ordinal_duration(chip, ordinal);
 	do {
-		u8 status = chip->ops->status(chip);
+		status = tpm_chip_status(chip);
 		if ((status & chip->ops->req_complete_mask) ==
 		    chip->ops->req_complete_val)
 			goto out_recv;
 
-		if (chip->ops->req_canceled(chip, status)) {
+		if (tpm_chip_req_canceled(chip, status)) {
 			dev_err(&chip->dev, "Operation Canceled\n");
 			return -ECANCELED;
 		}
@@ -118,7 +143,7 @@ static ssize_t tpm_try_transmit(struct tpm_chip *chip, void *buf, size_t bufsiz)
 		rmb();
 	} while (time_before(jiffies, stop));
 
-	chip->ops->cancel(chip);
+	tpm_chip_cancel(chip);
 	dev_err(&chip->dev, "Operation Timed out\n");
 	return -ETIME;
 
diff --git a/drivers/char/tpm/tpm_ftpm_tee.c b/drivers/char/tpm/tpm_ftpm_tee.c
index 8d9209dfc384..3732f3623537 100644
--- a/drivers/char/tpm/tpm_ftpm_tee.c
+++ b/drivers/char/tpm/tpm_ftpm_tee.c
@@ -164,30 +164,12 @@ static int ftpm_tee_tpm_op_send(struct tpm_chip *chip, u8 *buf, size_t len)
 	return 0;
 }
 
-static void ftpm_tee_tpm_op_cancel(struct tpm_chip *chip)
-{
-	/* not supported */
-}
-
-static u8 ftpm_tee_tpm_op_status(struct tpm_chip *chip)
-{
-	return 0;
-}
-
-static bool ftpm_tee_tpm_req_canceled(struct tpm_chip *chip, u8 status)
-{
-	return false;
-}
-
 static const struct tpm_class_ops ftpm_tee_tpm_ops = {
 	.flags = TPM_OPS_AUTO_STARTUP,
 	.recv = ftpm_tee_tpm_op_recv,
 	.send = ftpm_tee_tpm_op_send,
-	.cancel = ftpm_tee_tpm_op_cancel,
-	.status = ftpm_tee_tpm_op_status,
 	.req_complete_mask = 0,
 	.req_complete_val = 0,
-	.req_canceled = ftpm_tee_tpm_req_canceled,
 };
 
 /*
-- 
2.39.5