re: spi: bcm2835: fix gpio cs level inversion

[Colin Ian King]

Hi,

Static analysis with coverity on today's linux-next has detected a
potential issue in  bcm2835_spi_setup() in the following commit:

commit 5e31ba0c0543a04483b53151eb5b7413efece94c
Author: Martin Hundebøll <martin@xxxxxxxxxx>
Date:   Wed Oct 14 11:02:30 2020 +0200

    spi: bcm2835: fix gpio cs level inversion

The analysis is as follows:

1191 static int bcm2835_spi_setup(struct spi_device *spi)
1192 {
1193        struct spi_controller *ctlr = spi->controller;
1194        struct bcm2835_spi *bs = spi_controller_get_devdata(ctlr);
1195        struct gpio_chip *chip;

1. var_decl: Declaring variable lflags without initializer.

... and later on ...

Uninitialized scalar variable (UNINIT)

9. uninit_use_in_call: Using uninitialized value lflags when calling
gpiochip_request_own_desc. [show details]

1262        spi->cs_gpiod = gpiochip_request_own_desc(chip, 8 -
spi->chip_select,
1263                                                  DRV_NAME,
1264                                                  lflags,
1265                                                  GPIOD_OUT_LOW);


The call to gpiochip_request_own_desc passes the uninitalized lflags
down to  gpiod_configure_flags:

int gpiod_configure_flags(struct gpio_desc *desc, const char *con_id,
3698                unsigned long lflags, enum gpiod_flags dflags)
3699{
3700        int ret;
3701
3702        if (lflags & GPIO_ACTIVE_LOW)
3703                set_bit(FLAG_ACTIVE_LOW, &desc->flags);
3704
3705        if (lflags & GPIO_OPEN_DRAIN)
3706                set_bit(FLAG_OPEN_DRAIN, &desc->flags);

so this looks like lflags needs to be initialized with something
legitimate, probably zero?

Colin