lib: check mezzanine presence before EEPROM read/write

Signed-off-by: Federico Vaga <federico.vaga@cern.ch>

lib/fmc/core.h

@@ -20,6 +20,7 @@ struct fmc_tkn;
 #define __FMC_ERR_MIN 4096
 enum fmc_error_numbers {
 	FMC_ERR_SLOT_NODEV = __FMC_ERR_MIN,
+	FMC_ERR_NOPRES,
 	__FMC_ERR_MAX,
 };
 

lib/libfmc.c

@@ -56,6 +56,7 @@ struct fmc_carrier {
 
 static const char *fmc_error_string[] = {
 	[FMC_ERR_SLOT_NODEV - __FMC_ERR_MIN] = "Slot number not found",
+	[FMC_ERR_NOPRES - __FMC_ERR_MIN] = "FMC Module not present",
 };
 
 /**
@@ -447,6 +448,11 @@ int fmc_slot_eeprom_read(struct fmc_tkn *tkn, unsigned int slot_n,
 	int fd;
 	int ret;
 
+	if (!fmc_slot_is_present(tkn, slot_n)) {
+		errno = FMC_ERR_NOPRES;
+		return -1;
+	}
+
 	snprintf(path, MAX_PATH_LEN,
 		 "/sys/class/fmc/fmc-carrier-%u/fmc-slot-%u.%u/fru_eeprom/eeprom",
 		 carrier->id, carrier->id, slot_n);
@@ -480,6 +486,11 @@ int fmc_slot_eeprom_write(struct fmc_tkn *tkn, unsigned int slot_n,
 	int fd;
 	int ret;
 
+	if (!fmc_slot_is_present(tkn, slot_n)) {
+		errno = FMC_ERR_NOPRES;
+		return -1;
+	}
+
 	snprintf(path, MAX_PATH_LEN,
 		 "/sys/class/fmc/fmc-carrier-%u/fmc-slot-%u.%u/fru_eeprom/eeprom",
 		 carrier->id, carrier->id, slot_n);