PCIER_SLOT_CTL
#define PCI_EXP_SLTCTL PCIER_SLOT_CTL /* Slot Control */
WREG(PCIER_SLOT_CTL, cfg->pcie_slot_ctl);
cfg->pcie_slot_ctl = RREG(PCIER_SLOT_CTL);
ctl = pcie_read_config(dev, PCIER_SLOT_CTL, 2);
pcie_write_config(dev, PCIER_SLOT_CTL, new, 2);
ctl = read_config(fd, &p->pc_sel, ptr + PCIER_SLOT_CTL, 2);