On Mon, 15 Oct 2018, Hannes Reinecke wrote:
In the case of send_cmd_residual, that would mean a second #ifdef
added to esp_data_bytes_sent() where it gets used. I'm happy to comply
but I fear that all these #ifdefs may harm readability...
There are already other variables in struct esp that may go unused,
such as dma_regs, that don't have #ifdefs to elide them. Are these
also problematic in some way?
The unused fields in the struct are not so much an issue; in fact, it
rather complicated things when having individual fields in the struct
surrounded by CONFIG_XXX, as then the order of the fields would change
depending on the configuration. Which makes it really hard to debug ..
True enough. We agree that this #ifdef is undesirable. And yet when I
tried it, I found an unexpected readability benefit to your suggestion:
#ifdef CONFIG_SCSI_ESP_PIO
u8 __iomem *fifo_reg;
int send_cmd_error;
u32 send_cmd_residual;
#endif
This grouping does help convey the purpose of these struct members, even
though the #ifdef is meant for the compiler not for the human reader.
So maybe it makes sense to group these definitions (they are all the same
size):
/* These are used by esp_scsi_send_pio_cmd() */
u8 __iomem *fifo_reg;
int send_cmd_error;
u32 send_cmd_residual;
However, the function declaration really is a worry, as the actual
function body only exists when the config option is enabled. So either
add a dummy function or surround the function declaration by
CONFIG_ESP_PIO.
Otherwise I think Dan Carpenter and the likes are guaranteed to send you
a nice mail complaining about this ...
Do static checkers really complain about this? I think the validity of an
extern can't be known until the final linkage is done.
At that point the checker may complain that no compilation unit references
a symbol in a header.
But this would lead to false positives where a header file is shared by
separate programs which share library code but not macros.
--
Cheers,
Hannes
