/* * pcie.c * * Copyright (c) 2010 Isaku Yamahata * VA Linux Systems Japan K.K. * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation; either version 2 of the License, or * (at your option) any later version. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License along * with this program; if not, see . */ #include "qemu/osdep.h" #include "qemu-common.h" #include "hw/pci/pci_bridge.h" #include "hw/pci/pcie.h" #include "hw/pci/msix.h" #include "hw/pci/msi.h" #include "hw/pci/pci_bus.h" #include "hw/pci/pcie_regs.h" #include "qemu/range.h" //#define DEBUG_PCIE #ifdef DEBUG_PCIE # define PCIE_DPRINTF(fmt, ...) \ fprintf(stderr, "%s:%d " fmt, __func__, __LINE__, ## __VA_ARGS__) #else # define PCIE_DPRINTF(fmt, ...) do {} while (0) #endif #define PCIE_DEV_PRINTF(dev, fmt, ...) \ PCIE_DPRINTF("%s:%x "fmt, (dev)->name, (dev)->devfn, ## __VA_ARGS__) /*************************************************************************** * pci express capability helper functions */ int pcie_cap_init(PCIDevice *dev, uint8_t offset, uint8_t type, uint8_t port) { int pos; uint8_t *exp_cap; assert(pci_is_express(dev)); pos = pci_add_capability(dev, PCI_CAP_ID_EXP, offset, PCI_EXP_VER2_SIZEOF); if (pos < 0) { return pos; } dev->exp.exp_cap = pos; exp_cap = dev->config + pos; /* capability register interrupt message number defaults to 0 */ pci_set_word(exp_cap + PCI_EXP_FLAGS, ((type << PCI_EXP_FLAGS_TYPE_SHIFT) & PCI_EXP_FLAGS_TYPE) | PCI_EXP_FLAGS_VER2); /* device capability register * table 7-12: * roll based error reporting bit must be set by all * Functions conforming to the ECN, PCI Express Base * Specification, Revision 1.1., or subsequent PCI Express Base * Specification revisions. */ pci_set_long(exp_cap + PCI_EXP_DEVCAP, PCI_EXP_DEVCAP_RBER); pci_set_long(exp_cap + PCI_EXP_LNKCAP, (port << PCI_EXP_LNKCAP_PN_SHIFT) | PCI_EXP_LNKCAP_ASPMS_0S | PCI_EXP_LNK_MLW_1 | PCI_EXP_LNK_LS_25); pci_set_word(exp_cap + PCI_EXP_LNKSTA, PCI_EXP_LNK_MLW_1 | PCI_EXP_LNK_LS_25 |PCI_EXP_LNKSTA_DLLLA); pci_set_long(exp_cap + PCI_EXP_DEVCAP2, PCI_EXP_DEVCAP2_EFF | PCI_EXP_DEVCAP2_EETLPP); pci_set_word(dev->wmask + pos + PCI_EXP_DEVCTL2, PCI_EXP_DEVCTL2_EETLPPB); return pos; } int pcie_endpoint_cap_init(PCIDevice *dev, uint8_t offset) { uint8_t type = PCI_EXP_TYPE_ENDPOINT; /* * Windows guests will report Code 10, device cannot start, if * a regular Endpoint type is exposed on a root complex. These * should instead be Root Complex Integrated Endpoints. */ if (pci_bus_is_express(dev->bus) && pci_bus_is_root(dev->bus)) { type = PCI_EXP_TYPE_RC_END; } return pcie_cap_init(dev, offset, type, 0); } void pcie_cap_exit(PCIDevice *dev) { pci_del_capability(dev, PCI_CAP_ID_EXP, PCI_EXP_VER2_SIZEOF); } uint8_t pcie_cap_get_type(const PCIDevice *dev) { uint32_t pos = dev->exp.exp_cap; assert(pos > 0); return (pci_get_word(dev->config + pos + PCI_EXP_FLAGS) & PCI_EXP_FLAGS_TYPE) >> PCI_EXP_FLAGS_TYPE_SHIFT; } /* MSI/MSI-X */ /* pci express interrupt message number */ /* 7.8.2 PCI Express Capabilities Register: Interrupt Message Number */ void pcie_cap_flags_set_vector(PCIDevice *dev, uint8_t vector) { uint8_t *exp_cap = dev->config + dev->exp.exp_cap; assert(vector < 32); pci_word_test_and_clear_mask(exp_cap + PCI_EXP_FLAGS, PCI_EXP_FLAGS_IRQ); pci_word_test_and_set_mask(exp_cap + PCI_EXP_FLAGS, vector << PCI_EXP_FLAGS_IRQ_SHIFT); } uint8_t pcie_cap_flags_get_vector(PCIDevice *dev) { return (pci_get_word(dev->config + dev->exp.exp_cap + PCI_EXP_FLAGS) & PCI_EXP_FLAGS_IRQ) >> PCI_EXP_FLAGS_IRQ_SHIFT; } void pcie_cap_deverr_init(PCIDevice *dev) { uint32_t pos = dev->exp.exp_cap; pci_long_test_and_set_mask(dev->config + pos + PCI_EXP_DEVCAP, PCI_EXP_DEVCAP_RBER); pci_long_test_and_set_mask(dev->wmask + pos + PCI_EXP_DEVCTL, PCI_EXP_DEVCTL_CERE | PCI_EXP_DEVCTL_NFERE | PCI_EXP_DEVCTL_FERE | PCI_EXP_DEVCTL_URRE); pci_long_test_and_set_mask(dev->w1cmask + pos + PCI_EXP_DEVSTA, PCI_EXP_DEVSTA_CED | PCI_EXP_DEVSTA_NFED | PCI_EXP_DEVSTA_FED | PCI_EXP_DEVSTA_URD); } void pcie_cap_deverr_reset(PCIDevice *dev) { uint8_t *devctl = dev->config + dev->exp.exp_cap + PCI_EXP_DEVCTL; pci_long_test_and_clear_mask(devctl, PCI_EXP_DEVCTL_CERE | PCI_EXP_DEVCTL_NFERE | PCI_EXP_DEVCTL_FERE | PCI_EXP_DEVCTL_URRE); } static void hotplug_event_update_event_status(PCIDevice *dev) { uint32_t pos = dev->exp.exp_cap; uint8_t *exp_cap = dev->config + pos; uint16_t sltctl = pci_get_word(exp_cap + PCI_EXP_SLTCTL); uint16_t sltsta = pci_get_word(exp_cap + PCI_EXP_SLTSTA); dev->exp.hpev_notified = (sltctl & PCI_EXP_SLTCTL_HPIE) && (sltsta & sltctl & PCI_EXP_HP_EV_SUPPORTED); } static void hotplug_event_notify(PCIDevice *dev) { bool prev = dev->exp.hpev_notified; hotplug_event_update_event_status(dev); if (prev == dev->exp.hpev_notified) { return; } /* Note: the logic above does not take into account whether interrupts * are masked. The result is that interrupt will be sent when it is * subsequently unmasked. This appears to be legal: Section 6.7.3.4: * The Port may optionally send an MSI when there are hot-plug events that * occur while interrupt generation is disabled, and interrupt generation is * subsequently enabled. */ if (msix_enabled(dev)) { msix_notify(dev, pcie_cap_flags_get_vector(dev)); } else if (msi_enabled(dev)) { msi_notify(dev, pcie_cap_flags_get_vector(dev)); } else { pci_set_irq(dev, dev->exp.hpev_notified); } } static void hotplug_event_clear(PCIDevice *dev) { hotplug_event_update_event_status(dev); if (!msix_enabled(dev) && !msi_enabled(dev) && !dev->exp.hpev_notified) { pci_irq_deassert(dev); } } /* * A PCI Express Hot-Plug Event has occurred, so update slot status register * and notify OS of the event if necessary. * * 6.7.3 PCI Express Hot-Plug Events * 6.7.3.4 Software Notification of Hot-Plug Events */ static void pcie_cap_slot_event(PCIDevice *dev, PCIExpressHotPlugEvent event) { /* Minor optimization: if nothing changed - no event is needed. */ if (pci_word_test_and_set_mask(dev->config + dev->exp.exp_cap + PCI_EXP_SLTSTA, event)) { return; } hotplug_event_notify(dev); } static void pcie_cap_slot_hotplug_common(PCIDevice *hotplug_dev, DeviceState *dev, uint8_t **exp_cap, Error **errp) { *exp_cap = hotplug_dev->config + hotplug_dev->exp.exp_cap; uint16_t sltsta = pci_get_word(*exp_cap + PCI_EXP_SLTSTA); PCIE_DEV_PRINTF(PCI_DEVICE(dev), "hotplug state: 0x%x\n", sltsta); if (sltsta & PCI_EXP_SLTSTA_EIS) { /* the slot is electromechanically locked. * This error is propagated up to qdev and then to HMP/QMP. */ error_setg_errno(errp, EBUSY, "slot is electromechanically locked"); } } void pcie_cap_slot_hotplug_cb(HotplugHandler *hotplug_dev, DeviceState *dev, Error **errp) { uint8_t *exp_cap; PCIDevice *pci_dev = PCI_DEVICE(dev); pcie_cap_slot_hotplug_common(PCI_DEVICE(hotplug_dev), dev, &exp_cap, errp); /* Don't send event when device is enabled during qemu machine creation: * it is present on boot, no hotplug event is necessary. We do send an * event when the device is disabled later. */ if (!dev->hotplugged) { pci_word_test_and_set_mask(exp_cap + PCI_EXP_SLTSTA, PCI_EXP_SLTSTA_PDS); return; } /* To enable multifunction hot-plug, we just ensure the function * 0 added last. When function 0 is added, we set the sltsta and * inform OS via event notification. */ if (pci_get_function_0(pci_dev)) { pci_word_test_and_set_mask(exp_cap + PCI_EXP_SLTSTA, PCI_EXP_SLTSTA_PDS); pcie_cap_slot_event(PCI_DEVICE(hotplug_dev), PCI_EXP_HP_EV_PDC | PCI_EXP_HP_EV_ABP); } } static void pcie_unplug_device(PCIBus *bus, PCIDevice *dev, void *opaque) { object_unparent(OBJECT(dev)); } void pcie_cap_slot_hot_unplug_request_cb(HotplugHandler *hotplug_dev, DeviceState *dev, Error **errp) { uint8_t *exp_cap; PCIDevice *pci_dev = PCI_DEVICE(dev); PCIBus *bus = pci_dev->bus; pcie_cap_slot_hotplug_common(PCI_DEVICE(hotplug_dev), dev, &exp_cap, errp); /* In case user cancel the operation of multi-function hot-add, * remove the function that is unexposed to guest individually, * without interaction with guest. */ if (pci_dev->devfn && !bus->devices[0]) { pcie_unplug_device(bus, pci_dev, NULL); return; } pcie_cap_slot_push_attention_button(PCI_DEVICE(hotplug_dev)); } /* pci express slot for pci express root/downstream port PCI express capability slot registers */ void pcie_cap_slot_init(PCIDevice *dev, uint16_t slot) { uint32_t pos = dev->exp.exp_cap; pci_word_test_and_set_mask(dev->config + pos + PCI_EXP_FLAGS, PCI_EXP_FLAGS_SLOT); pci_long_test_and_clear_mask(dev->config + pos + PCI_EXP_SLTCAP, ~PCI_EXP_SLTCAP_PSN); pci_long_test_and_set_mask(dev->config + pos + PCI_EXP_SLTCAP, (slot << PCI_EXP_SLTCAP_PSN_SHIFT) | PCI_EXP_SLTCAP_EIP | PCI_EXP_SLTCAP_HPS | PCI_EXP_SLTCAP_HPC | PCI_EXP_SLTCAP_PIP | PCI_EXP_SLTCAP_AIP | PCI_EXP_SLTCAP_ABP); if (dev->cap_present & QEMU_PCIE_SLTCAP_PCP) { pci_long_test_and_set_mask(dev->config + pos + PCI_EXP_SLTCAP, PCI_EXP_SLTCAP_PCP); pci_word_test_and_clear_mask(dev->config + pos + PCI_EXP_SLTCTL, PCI_EXP_SLTCTL_PCC); pci_word_test_and_set_mask(dev->wmask + pos + PCI_EXP_SLTCTL, PCI_EXP_SLTCTL_PCC); } pci_word_test_and_clear_mask(dev->config + pos + PCI_EXP_SLTCTL, PCI_EXP_SLTCTL_PIC | PCI_EXP_SLTCTL_AIC); pci_word_test_and_set_mask(dev->config + pos + PCI_EXP_SLTCTL, PCI_EXP_SLTCTL_PIC_OFF | PCI_EXP_SLTCTL_AIC_OFF); pci_word_test_and_set_mask(dev->wmask + pos + PCI_EXP_SLTCTL, PCI_EXP_SLTCTL_PIC | PCI_EXP_SLTCTL_AIC | PCI_EXP_SLTCTL_HPIE | PCI_EXP_SLTCTL_CCIE | PCI_EXP_SLTCTL_PDCE | PCI_EXP_SLTCTL_ABPE); /* Although reading PCI_EXP_SLTCTL_EIC returns always 0, * make the bit writable here in order to detect 1b is written. * pcie_cap_slot_write_config() test-and-clear the bit, so * this bit always returns 0 to the guest. */ pci_word_test_and_set_mask(dev->wmask + pos + PCI_EXP_SLTCTL, PCI_EXP_SLTCTL_EIC); pci_word_test_and_set_mask(dev->w1cmask + pos + PCI_EXP_SLTSTA, PCI_EXP_HP_EV_SUPPORTED); dev->exp.hpev_notified = false; qbus_set_hotplug_handler(BUS(pci_bridge_get_sec_bus(PCI_BRIDGE(dev))), DEVICE(dev), NULL); } void pcie_cap_slot_reset(PCIDevice *dev) { uint8_t *exp_cap = dev->config + dev->exp.exp_cap; uint8_t port_type = pcie_cap_get_type(dev); assert(port_type == PCI_EXP_TYPE_DOWNSTREAM || port_type == PCI_EXP_TYPE_ROOT_PORT); PCIE_DEV_PRINTF(dev, "reset\n"); pci_word_test_and_clear_mask(exp_cap + PCI_EXP_SLTCTL, PCI_EXP_SLTCTL_EIC | PCI_EXP_SLTCTL_PIC | PCI_EXP_SLTCTL_AIC | PCI_EXP_SLTCTL_HPIE | PCI_EXP_SLTCTL_CCIE | PCI_EXP_SLTCTL_PDCE | PCI_EXP_SLTCTL_ABPE); pci_word_test_and_set_mask(exp_cap + PCI_EXP_SLTCTL, PCI_EXP_SLTCTL_AIC_OFF); if (dev->cap_present & QEMU_PCIE_SLTCAP_PCP) { /* Downstream ports enforce device number 0. */ bool populated = pci_bridge_get_sec_bus(PCI_BRIDGE(dev))->devices[0]; uint16_t pic; if (populated) { pci_word_test_and_clear_mask(exp_cap + PCI_EXP_SLTCTL, PCI_EXP_SLTCTL_PCC); } else { pci_word_test_and_set_mask(exp_cap + PCI_EXP_SLTCTL, PCI_EXP_SLTCTL_PCC); } pic = populated ? PCI_EXP_SLTCTL_PIC_ON : PCI_EXP_SLTCTL_PIC_OFF; pci_word_test_and_set_mask(exp_cap + PCI_EXP_SLTCTL, pic); } pci_word_test_and_clear_mask(exp_cap + PCI_EXP_SLTSTA, PCI_EXP_SLTSTA_EIS |/* on reset, the lock is released */ PCI_EXP_SLTSTA_CC | PCI_EXP_SLTSTA_PDC | PCI_EXP_SLTSTA_ABP); hotplug_event_update_event_status(dev); } void pcie_cap_slot_write_config(PCIDevice *dev, uint32_t addr, uint32_t val, int len) { uint32_t pos = dev->exp.exp_cap; uint8_t *exp_cap = dev->config + pos; uint16_t sltsta = pci_get_word(exp_cap + PCI_EXP_SLTSTA); if (ranges_overlap(addr, len, pos + PCI_EXP_SLTSTA, 2)) { hotplug_event_clear(dev); } if (!ranges_overlap(addr, len, pos + PCI_EXP_SLTCTL, 2)) { return; } if (pci_word_test_and_clear_mask(exp_cap + PCI_EXP_SLTCTL, PCI_EXP_SLTCTL_EIC)) { sltsta ^= PCI_EXP_SLTSTA_EIS; /* toggle PCI_EXP_SLTSTA_EIS bit */ pci_set_word(exp_cap + PCI_EXP_SLTSTA, sltsta); PCIE_DEV_PRINTF(dev, "PCI_EXP_SLTCTL_EIC: " "sltsta -> 0x%02"PRIx16"\n", sltsta); } /* * If the slot is polulated, power indicator is off and power * controller is off, it is safe to detach the devices. */ if ((sltsta & PCI_EXP_SLTSTA_PDS) && (val & PCI_EXP_SLTCTL_PCC) && ((val & PCI_EXP_SLTCTL_PIC_OFF) == PCI_EXP_SLTCTL_PIC_OFF)) { PCIBus *sec_bus = pci_bridge_get_sec_bus(PCI_BRIDGE(dev)); pci_for_each_device(sec_bus, pci_bus_num(sec_bus), pcie_unplug_device, NULL); pci_word_test_and_clear_mask(exp_cap + PCI_EXP_SLTSTA, PCI_EXP_SLTSTA_PDS); pci_word_test_and_set_mask(exp_cap + PCI_EXP_SLTSTA, PCI_EXP_SLTSTA_PDC); } hotplug_event_notify(dev); /* * 6.7.3.2 Command Completed Events * * Software issues a command to a hot-plug capable Downstream Port by * issuing a write transaction that targets any portion of the Port’s Slot * Control register. A single write to the Slot Control register is * considered to be a single command, even if the write affects more than * one field in the Slot Control register. In response to this transaction, * the Port must carry out the requested actions and then set the * associated status field for the command completed event. */ /* Real hardware might take a while to complete requested command because * physical movement would be involved like locking the electromechanical * lock. However in our case, command is completed instantaneously above, * so send a command completion event right now. */ pcie_cap_slot_event(dev, PCI_EXP_HP_EV_CCI); } int pcie_cap_slot_post_load(void *opaque, int version_id) { PCIDevice *dev = opaque; hotplug_event_update_event_status(dev); return 0; } void pcie_cap_slot_push_attention_button(PCIDevice *dev) { pcie_cap_slot_event(dev, PCI_EXP_HP_EV_ABP); } /* root control/capabilities/status. PME isn't emulated for now */ void pcie_cap_root_init(PCIDevice *dev) { pci_set_word(dev->wmask + dev->exp.exp_cap + PCI_EXP_RTCTL, PCI_EXP_RTCTL_SECEE | PCI_EXP_RTCTL_SENFEE | PCI_EXP_RTCTL_SEFEE); } void pcie_cap_root_reset(PCIDevice *dev) { pci_set_word(dev->config + dev->exp.exp_cap + PCI_EXP_RTCTL, 0); } /* function level reset(FLR) */ void pcie_cap_flr_init(PCIDevice *dev) { pci_long_test_and_set_mask(dev->config + dev->exp.exp_cap + PCI_EXP_DEVCAP, PCI_EXP_DEVCAP_FLR); /* Although reading BCR_FLR returns always 0, * the bit is made writable here in order to detect the 1b is written * pcie_cap_flr_write_config() test-and-clear the bit, so * this bit always returns 0 to the guest. */ pci_word_test_and_set_mask(dev->wmask + dev->exp.exp_cap + PCI_EXP_DEVCTL, PCI_EXP_DEVCTL_BCR_FLR); } void pcie_cap_flr_write_config(PCIDevice *dev, uint32_t addr, uint32_t val, int len) { uint8_t *devctl = dev->config + dev->exp.exp_cap + PCI_EXP_DEVCTL; if (pci_get_word(devctl) & PCI_EXP_DEVCTL_BCR_FLR) { /* Clear PCI_EXP_DEVCTL_BCR_FLR after invoking the reset handler so the handler can detect FLR by looking at this bit. */ pci_device_reset(dev); pci_word_test_and_clear_mask(devctl, PCI_EXP_DEVCTL_BCR_FLR); } } /* Alternative Routing-ID Interpretation (ARI) * forwarding support for root and downstream ports */ void pcie_cap_arifwd_init(PCIDevice *dev) { uint32_t pos = dev->exp.exp_cap; pci_long_test_and_set_mask(dev->config + pos + PCI_EXP_DEVCAP2, PCI_EXP_DEVCAP2_ARI); pci_long_test_and_set_mask(dev->wmask + pos + PCI_EXP_DEVCTL2, PCI_EXP_DEVCTL2_ARI); } void pcie_cap_arifwd_reset(PCIDevice *dev) { uint8_t *devctl2 = dev->config + dev->exp.exp_cap + PCI_EXP_DEVCTL2; pci_long_test_and_clear_mask(devctl2, PCI_EXP_DEVCTL2_ARI); } bool pcie_cap_is_arifwd_enabled(const PCIDevice *dev) { if (!pci_is_express(dev)) { return false; } if (!dev->exp.exp_cap) { return false; } return pci_get_long(dev->config + dev->exp.exp_cap + PCI_EXP_DEVCTL2) & PCI_EXP_DEVCTL2_ARI; } /************************************************************************** * pci express extended capability list management functions * uint16_t ext_cap_id (16 bit) * uint8_t cap_ver (4 bit) * uint16_t cap_offset (12 bit) * uint16_t ext_cap_size */ static uint16_t pcie_find_capability_list(PCIDevice *dev, uint16_t cap_id, uint16_t *prev_p) { uint16_t prev = 0; uint16_t next; uint32_t header = pci_get_long(dev->config + PCI_CONFIG_SPACE_SIZE); if (!header) { /* no extended capability */ next = 0; goto out; } for (next = PCI_CONFIG_SPACE_SIZE; next; prev = next, next = PCI_EXT_CAP_NEXT(header)) { assert(next >= PCI_CONFIG_SPACE_SIZE); assert(next <= PCIE_CONFIG_SPACE_SIZE - 8); header = pci_get_long(dev->config + next); if (PCI_EXT_CAP_ID(header) == cap_id) { break; } } out: if (prev_p) { *prev_p = prev; } return next; } uint16_t pcie_find_capability(PCIDevice *dev, uint16_t cap_id) { return pcie_find_capability_list(dev, cap_id, NULL); } static void pcie_ext_cap_set_next(PCIDevice *dev, uint16_t pos, uint16_t next) { uint32_t header = pci_get_long(dev->config + pos); assert(!(next & (PCI_EXT_CAP_ALIGN - 1))); header = (header & ~PCI_EXT_CAP_NEXT_MASK) | ((next << PCI_EXT_CAP_NEXT_SHIFT) & PCI_EXT_CAP_NEXT_MASK); pci_set_long(dev->config + pos, header); } /* * caller must supply valid (offset, size) * such that the range shouldn't * overlap with other capability or other registers. * This function doesn't check it. */ void pcie_add_capability(PCIDevice *dev, uint16_t cap_id, uint8_t cap_ver, uint16_t offset, uint16_t size) { uint32_t header; uint16_t next; assert(offset >= PCI_CONFIG_SPACE_SIZE); assert(offset < offset + size); assert(offset + size <= PCIE_CONFIG_SPACE_SIZE); assert(size >= 8); assert(pci_is_express(dev)); if (offset == PCI_CONFIG_SPACE_SIZE) { header = pci_get_long(dev->config + offset); next = PCI_EXT_CAP_NEXT(header); } else { uint16_t prev; /* 0 is reserved cap id. use internally to find the last capability in the linked list */ next = pcie_find_capability_list(dev, 0, &prev); assert(prev >= PCI_CONFIG_SPACE_SIZE); assert(next == 0); pcie_ext_cap_set_next(dev, prev, offset); } pci_set_long(dev->config + offset, PCI_EXT_CAP(cap_id, cap_ver, next)); /* Make capability read-only by default */ memset(dev->wmask + offset, 0, size); memset(dev->w1cmask + offset, 0, size); /* Check capability by default */ memset(dev->cmask + offset, 0xFF, size); } /************************************************************************** * pci express extended capability helper functions */ /* ARI */ void pcie_ari_init(PCIDevice *dev, uint16_t offset, uint16_t nextfn) { pcie_add_capability(dev, PCI_EXT_CAP_ID_ARI, PCI_ARI_VER, offset, PCI_ARI_SIZEOF); pci_set_long(dev->config + offset + PCI_ARI_CAP, (nextfn & 0xff) << 8); }