Apple seems to be having trouble feeding the demand for iPhones in advance of the holiday selling season, according to a “CNNMoney” report.

Rodman & Renshaw’s Ashok Kumar told clients that low yields on an unidentified “key component” is likely to constrain production of the iPhone 4S this quarter. Still, overall iPhone shipments in the December quarter could come in around 30 million units, he said.

Meanwhile, Susquehanna analystJeff Fidacaro cites “supply constraints” in a report that suggests a 2-3 million reduction in iPhone 4S builds for the quarter, notes “CNNMoney.” He’s reducing his iPhone 4S production estimates from 26-28 million to 23-25 million.