RE: [tpmdd-devel] [PATCH 1/1] TPM: STMicroelectronics st33 driverSPI

From: Mathias LEBLANC
Date: Thu May 16 2013 - 05:05:36 EST

Hi Peter,
Thanks for your feedback.

You are right, this function looks like the spi_sync_transfer;
So, I will use it in the next version of the driver.

Regarding the while loop, I don't see how can I check the number of dummy byte differently?

For the module error, Yes I have modified the patch file :s, apparently I haven't correctly modified the number of lines

Finaly, These sparse warning are finaly fix ;).

Best regards,

Mathias Leblanc
From: Peter Hüwe [PeterHuewe@xxxxxx]
Sent: 16 May 2013 00:29
To: tpmdd-devel@xxxxxxxxxxxxxxxxxxxxx
Cc: Mathias LEBLANC; Kent Yoder; Rajiv Andrade; Marcel Selhorst; Sirrix AG; Jean-Luc BLANC; linux-kernel@xxxxxxxxxxxxxxx
Subject: Re: [tpmdd-devel] [PATCH 1/1] TPM: STMicroelectronics st33 driver SPI

Hi Matthias,

Am Mittwoch, 15. Mai 2013, 15:53:19 schrieb Matthias Leblanc:

> +static inline int spi_read_write(struct spi_device *spi,
> + struct spi_transfer xfer) {
> + struct spi_message msg;
> + spi_message_init(&msg);
> + spi_message_add_tail(&xfer, &msg);
> + return spi_sync(spi, &msg);
> +}

This looks extremely like the predefined spi_sync_transfer in include/linux/spi.h

* spi_sync_transfer - synchronous SPI data transfer
* @spi: device with which data will be exchanged
* @xfers: An array of spi_transfers
* @num_xfers: Number of items in the xfer array
* Context: can sleep
* Does a synchronous SPI data transfer of the given spi_transfer array.
* For more specific semantics see spi_sync().
* It returns zero on success, else a negative error code.
static inline int
spi_sync_transfer(struct spi_device *spi, struct spi_transfer *xfers,
unsigned int num_xfers)
struct spi_message msg;

spi_message_init_with_transfers(&msg, xfers, num_xfers);

return spi_sync(spi, &msg);

where spi_message_init_with_transfers is defined as

static inline void
spi_message_init_with_transfers(struct spi_message *m,
struct spi_transfer *xfers, unsigned int num_xfers)
unsigned int i;

for (i = 0; i < num_xfers; ++i)
spi_message_add_tail(&xfers[i], m);

If you combine these functions you end up (more or less) with your implementation

So please use spi_sync_transfer
OR as an alternative use spi_write / spi_read as an alternative as mentioned in a previous email

And here is a rather subjective remark:

> + for (; nbr_dummy_bytes < total_length &&
> + ((u8 *)xfer.rx_buf)[nbr_dummy_bytes] == 0;
> + nbr_dummy_bytes++)
> + ;

Not sure if it would be easier to read using a while and putting the increment
into the loop body

>+ while (nbr_dummy_bytes < total_length &&
>+ ((u8 *)xfer.rx_buf)[nbr_dummy_bytes] == 0)
>+ nbr_dummy_bytes++;

I usually don't like empty loop bodies, as they tend to be overlooked.

> +module_spi_driver(tpm_st33_spi_driver);
> +
> +MODULE_AUTHOR("Christophe Ricard (tpmsupport@xxxxxx)");
> +MODULE_VERSION("1.2.0");

Something is strange here - if I apply your patch, the module license gets lost - so I get a compile warning:

WARNING: modpost: missing MODULE_LICENSE() in /data/data-old/linux-2.6/drivers/char/tpm/tpm_spi_stm_st33.o

Do you edit the patch by hand before sending?

Steps to reproduce:
drivers/char/tpm $ git reset --hard tpmdd/tpmdd-04-26-13
HEAD is now at d224213 tpm_tis: missing platform_driver_unregister() on error in init_tis()
drivers/char/tpm $ git am /tmp/\[tpmdd-devel\]\ \[PATCH\ 1_1\]\ TPM_STMicroelectronics\ st33\ driver\ SPI.mbox
Applying: TPM: STMicroelectronics st33 driver SPI

drivers/char/tpm $ tail tpm_spi_stm_st33.c },
.probe = tpm_st33_spi_probe,
.remove = tpm_st33_spi_remove,


MODULE_AUTHOR("Christophe Ricard (tpmsupport@xxxxxx)");

And the usual sparse warnings ;)
drivers/char/tpm $ make M=`pwd` -C /data/data-old/linux-2.6/ modules C=1 CHECK=sparse
make: Entering directory `/data/data-old/linux-2.6'
CHECK /data/data-old/linux-2.6/drivers/char/tpm/tpm_spi_stm_st33.c
/data/data-old/linux-2.6/drivers/char/tpm/tpm_spi_stm_st33.c:104:35: warning: cast removes address space of expression
/data/data-old/linux-2.6/drivers/char/tpm/tpm_spi_stm_st33.c:170:35: warning: cast removes address space of expression
/data/data-old/linux-2.6/drivers/char/tpm/tpm_spi_stm_st33.c:242:19: warning: cast removes address space of expression
/data/data-old/linux-2.6/drivers/char/tpm/tpm_spi_stm_st33.c:235:15: warning: symbol 'wait_for_serirq_timeout' was not declared. Should it be static?
/data/data-old/linux-2.6/drivers/char/tpm/tpm_spi_stm_st33.c:482:19: warning: cast removes address space of expression

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