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Date: Mon, 26 Apr 2021 09:46:21 +0200
From: Jonathan Neuschäfer <j.neuschaefer@....net>
To: Emmanuel Gil Peyrot <linkmauve@...kmauve.fr>
Cc: Arnd Bergmann <arnd@...db.de>,
Jonathan Neuschäfer <j.ne@...teo.net>,
linux-kernel@...r.kernel.org,
Jonathan Neuschäfer <j.neuschaefer@....net>,
Rob Herring <robh+dt@...nel.org>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Aswath Govindraju <a-govindraju@...com>,
Vadym Kochan <vadym.kochan@...ision.eu>,
devicetree@...r.kernel.org
Subject: Re: [PATCH v2 1/3] misc: eeprom_93xx46: Remove hardcoded bit lengths
On Sat, Apr 24, 2021 at 11:25:41PM +0200, Emmanuel Gil Peyrot wrote:
> This avoids using magic numbers based on the length of an address or a
> command, while we only want to differentiate between 8-bit and 16-bit.
>
> The driver was previously wrapping around the offset in the write
> operation, this now returns -EINVAL instead (but should never happen in
> the first place).
>
> If two pointer indirections are too many, we could move the flags to the
> main struct instead, but I doubt it’s going to make any sensible
> difference on any hardware.
>
> Signed-off-by: Emmanuel Gil Peyrot <linkmauve@...kmauve.fr>
> ---
I'm not an EEPROM driver expert, but FWIW:
Reviewed-by: Jonathan Neuschäfer <j.neuschaefer@....net>
> drivers/misc/eeprom/eeprom_93xx46.c | 57 ++++++++++++++++-------------
> 1 file changed, 32 insertions(+), 25 deletions(-)
>
> diff --git a/drivers/misc/eeprom/eeprom_93xx46.c b/drivers/misc/eeprom/eeprom_93xx46.c
> index 80114f4c80ad..ffdb8e5a26e0 100644
> --- a/drivers/misc/eeprom/eeprom_93xx46.c
> +++ b/drivers/misc/eeprom/eeprom_93xx46.c
> @@ -9,6 +9,7 @@
> #include <linux/device.h>
> #include <linux/gpio/consumer.h>
> #include <linux/kernel.h>
> +#include <linux/log2.h>
> #include <linux/module.h>
> #include <linux/mutex.h>
> #include <linux/of.h>
> @@ -70,6 +71,7 @@ static int eeprom_93xx46_read(void *priv, unsigned int off,
> struct eeprom_93xx46_dev *edev = priv;
> char *buf = val;
> int err = 0;
> + int bits;
>
> if (unlikely(off >= edev->size))
> return 0;
> @@ -83,21 +85,21 @@ static int eeprom_93xx46_read(void *priv, unsigned int off,
> if (edev->pdata->prepare)
> edev->pdata->prepare(edev);
>
> + /* The opcode in front of the address is three bits. */
> + bits = edev->addrlen + 3;
> +
> while (count) {
> struct spi_message m;
> struct spi_transfer t[2] = { { 0 } };
> u16 cmd_addr = OP_READ << edev->addrlen;
> size_t nbytes = count;
> - int bits;
>
> - if (edev->addrlen == 7) {
> - cmd_addr |= off & 0x7f;
> - bits = 10;
> + if (edev->pdata->flags & EE_ADDR8) {
> + cmd_addr |= off;
> if (has_quirk_single_word_read(edev))
> nbytes = 1;
> } else {
> - cmd_addr |= (off >> 1) & 0x3f;
> - bits = 9;
> + cmd_addr |= (off >> 1);
> if (has_quirk_single_word_read(edev))
> nbytes = 2;
> }
> @@ -152,14 +154,14 @@ static int eeprom_93xx46_ew(struct eeprom_93xx46_dev *edev, int is_on)
> int bits, ret;
> u16 cmd_addr;
>
> + /* The opcode in front of the address is three bits. */
> + bits = edev->addrlen + 3;
> +
> cmd_addr = OP_START << edev->addrlen;
> - if (edev->addrlen == 7) {
> + if (edev->pdata->flags & EE_ADDR8)
> cmd_addr |= (is_on ? ADDR_EWEN : ADDR_EWDS) << 1;
> - bits = 10;
> - } else {
> + else
> cmd_addr |= (is_on ? ADDR_EWEN : ADDR_EWDS);
> - bits = 9;
> - }
>
> if (has_quirk_instruction_length(edev)) {
> cmd_addr <<= 2;
> @@ -205,15 +207,19 @@ eeprom_93xx46_write_word(struct eeprom_93xx46_dev *edev,
> int bits, data_len, ret;
> u16 cmd_addr;
>
> + if (unlikely(off >= edev->size))
> + return -EINVAL;
> +
> + /* The opcode in front of the address is three bits. */
> + bits = edev->addrlen + 3;
> +
> cmd_addr = OP_WRITE << edev->addrlen;
>
> - if (edev->addrlen == 7) {
> - cmd_addr |= off & 0x7f;
> - bits = 10;
> + if (edev->pdata->flags & EE_ADDR8) {
> + cmd_addr |= off;
> data_len = 1;
> } else {
> - cmd_addr |= (off >> 1) & 0x3f;
> - bits = 9;
> + cmd_addr |= (off >> 1);
> data_len = 2;
> }
>
> @@ -253,7 +259,7 @@ static int eeprom_93xx46_write(void *priv, unsigned int off,
> return count;
>
> /* only write even number of bytes on 16-bit devices */
> - if (edev->addrlen == 6) {
> + if (edev->pdata->flags & EE_ADDR16) {
> step = 2;
> count &= ~1;
> }
> @@ -295,14 +301,14 @@ static int eeprom_93xx46_eral(struct eeprom_93xx46_dev *edev)
> int bits, ret;
> u16 cmd_addr;
>
> + /* The opcode in front of the address is three bits. */
> + bits = edev->addrlen + 3;
> +
> cmd_addr = OP_START << edev->addrlen;
> - if (edev->addrlen == 7) {
> + if (edev->pdata->flags & EE_ADDR8)
> cmd_addr |= ADDR_ERAL << 1;
> - bits = 10;
> - } else {
> + else
> cmd_addr |= ADDR_ERAL;
> - bits = 9;
> - }
>
> if (has_quirk_instruction_length(edev)) {
> cmd_addr <<= 2;
> @@ -455,10 +461,12 @@ static int eeprom_93xx46_probe(struct spi_device *spi)
> if (!edev)
> return -ENOMEM;
>
> + edev->size = 128;
> +
> if (pd->flags & EE_ADDR8)
> - edev->addrlen = 7;
> + edev->addrlen = ilog2(edev->size);
> else if (pd->flags & EE_ADDR16)
> - edev->addrlen = 6;
> + edev->addrlen = ilog2(edev->size) - 1;
> else {
> dev_err(&spi->dev, "unspecified address type\n");
> return -EINVAL;
> @@ -469,7 +477,6 @@ static int eeprom_93xx46_probe(struct spi_device *spi)
> edev->spi = spi;
> edev->pdata = pd;
>
> - edev->size = 128;
> edev->nvmem_config.type = NVMEM_TYPE_EEPROM;
> edev->nvmem_config.name = dev_name(&spi->dev);
> edev->nvmem_config.dev = &spi->dev;
> --
> 2.31.1
>
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