Hello, I wrote:
That didn't stop you from using 'void *context' as an argument.
;-)
The void* that's "worse" is one that must only point to a
specific type of object. When the type has that kind of
restriction, using void* is nothing but bug-bait.
It's OK when the point is explicitly to pass around a handle
of arbitrary type, for interpretation by whatever provided it
in the first place -- the role of caller "context" in this and
many other interfaces.
You have yourself said that you'd like to use this approach
uniformly in several drivers -- which would naturally have different
device instance objects hiding behind 'void *'.
What I said was I wanted "struct at24_iface *" to
not be specific to the at24 driver. Maybe a
"struct persistent_memory *" or "struct blob *".
I don't know how you can turn that into "void *".
Passing "void *" is generally considered worse
Sigh, I never suggested that. :-/
What I suggested is using 'void *' to pass a pointer to device data
which 'struct at24_iface *' (or whatever the name will be) certainly
is not.
I wonder how many lines you were skipping reading my mails...
Foir the clarity, that's what I suggested after I'd agreed that
diurect exporting of read()/write() methods was undesirable:
static ssize_t at24_iface_read(void *data, char *buf, off_t offset, size_t
count)
{
return at24_eeprom_read((struct at24_data *)data, buf, offset, count);
}
static ssize_t at24_iface_write(void *data, char *buf, off_t offset, size_t
count)
{
return at24_eeprom_write((struct at24_data *)data, buf, offset, count);
}
static const struct at24_iface {
ssize_t (*read)(void *data, char *buf, off_t offset, size_t count);
ssize_t (*write)(void *data, char *buf, off_t offset, size_t count);
} at24_iface;
static int at24_probe(struct i2c_client *client, const struct i2c_device_id *id)
{
struct at24_platform_data chip;
[...]
/* export data to kernel code */
if (chip.setup)
chip.setup(&at24_iface, at24, chip.context);
return 0;
[...]
struct at24_platform_data {
u32 byte_len; /* size (sum of all addr) */
u16 page_size; /* for writes */
[...]
int (*setup)(struct at24_iface *iface, void *data, void
*context);
void *context;
};
WBR, Sergei
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