misc: eeprom_93xx46: Remove hardcoded bit lengths

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.

Reviewed-by: Jonathan Neuschäfer <j.neuschaefer@gmx.net>
Signed-off-by: Emmanuel Gil Peyrot <linkmauve@linkmauve.fr>
Link: https://lore.kernel.org/r/20210511210727.24895-2-linkmauve@linkmauve.fr
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/misc/eeprom/eeprom_93xx46.c b/drivers/misc/eeprom/eeprom_93xx46.c
index 80114f4c80ad36d8c510cb538734587b8d20d54a..ffdb8e5a26e09bbfec6d661f5a90e9948e333d00 100644 (file)
--- 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;